Western evaluation centre

During the middle of war, the small staff of the intercept and listening stations (German: Horchleitstelle) was found to be inadequate to cope with the large amount of traffic resulting from the pressures of the war. A central cryptanalytic agency was established in Berlin, around 1 February 1941, that was designated as Inspecktorate 7 or more simply In 7. It was also commanded by the Chief of the Army Equipment and Commander of the Replacement Army (German: Chef der Heeresrüstung und Befehlshaber des Ersatzheeres Inspektion 7 Gruppe VI), specifically Obstlt. Hassel. The experience of 1940 illustrated the fact that huge expansion of the German Army cryptologic effort was desirable. A central evaluation agency was created at the Zeppelin bunker near Zossen, which was designated as Control Station for Signal Intelligence (German: Leitstelle der Nachrichtenaufklärung) (abbr. LNA).

Gruppe VI of In 7 (In 7/VI) was organised by Major Mang, whose aim was to not only build staffing levels at the centre, but to provide reserves of staff that could be called upon when necessary. In order to provide sufficient staff, Mang subordinated the In 6/VI unit to Chief of the Army Equipment and Commander of the Replacement Army.^[35] In matters of policy, In 7/VI was subordinated to the Field Army only. Considered a curious form of organisation, it enabled the cryptanalytic service to recruit sufficient staff without operational interference, at the same time maintaining close support of field units.^[35] The cryptographic section would eventually become independent.^[35]

Eastern evaluation centre

During the first months of the unit, Russian cryptanalysis was conducted as part of the operational schedule of In 7/VI, with Russian evaluation included as part of the cryptanalytic work done by unit LNA. Both of these units felt, incorrectly, that cryptanalysis and evaluation of Russian intercepts should be carried out close to the front lines of the field army in East Prussia. This resulted in significant numbers of personnel being detached from the LNA and In 7/VI in late 1941, made up of cryptanalysts and evaluators skilled in Russian traffic and sent to Loetzen to work.^[35] This group would eventually become the nucleus of the organisation: Intercept Control Station East (German: Horchleitstelle Ost) (abbr. HLS Ost) for Russian evaluation and traffic analysis. From this point on until November 1944, signal intelligence was divided into Russian cryptanalysis carried out by HLS Ost, and non-Russian signal intelligence carried out by OKH/Chi and LNA.

Expansion

In 1942, the responsibility for security testing of existing German Army cryptographic systems had been transferred from In 7/IV to In 7/VI.^[36] From that time, the Army Signal Security Agency, In 7/IV had been confined to the development of new systems for the Army and for the production, printing, and distribution of current keys and systems.^[37]

In the autumn of 1943, OKH/Chi had been transferred to the newly created Department of Signals of the General Army Office and renamed Signal Intelligence, Department of Signals, General Army Office, Army High Command (German: Oberkommando des Heeres/Allgemeines Heeresamt/Amtsgruppe Nachrichten/Nachrichtenaufklärung) (abbr. OKH/AHA/AgN/NA). Minor changes in internal organisation were affected, but the function and operation of the agency was not changed.^[38]

Although there was no essential change in the organisation of the field units of Germany Army Sigint Service from 1941 to 1944, additional units were put in place in the field. In 1942, the eastern KONA units (1,2,3) were supplemented by the addition of KONA 6, which was formed to cover the German campaign in the Caucasus.^[39] The KONA unit was not subordinated to any Army Group but was directly under HLS Ost. KONA 7 was established in February 1943 and was subordinated to the Commander-in-Chief South, Albert Kesselring, who controlled Army Group C, and the German forces in Italy.^[40]

The organisation of the German Army Sigint Service in 1944 consisted of the following:^[41]

• A central cryptanalytic agency for non-Russian traffic: In 7/VI, later AgN/NA
• A central evaluation agency for non-Russian traffic: LNA
• A central cryptanalytic and evaluation agency for Russian traffic: HLS Ost
• Seven Signal Intelligence Regiments (KONA)
• An Army Signal Security agency for the distribution and development of Army systems: In 7/IV

Organisation of GDNA

Organisation chart of the GdNA

This organisation of OKH/GdNA was in effect from November 1944 to the end of the war. Approximately 700 people were employed by the unit.^{[57][note 1]}

• Headquarters Unit. The HQ unit of OKH/GDNA, was managed by (German: oberst) (colonel) Fritz Boetzel, his chief of staff, German: Oberleutnant (lieutenant colonel) Andrea, the Adjutant Lieutenant Moravec and staff officer Lieutenant (German: leutnant) Koebe. As well as all staff being subordinate to the unit, the unit also controlled two intercept stations, Feste 6 and Feste 11 (KONA Unit), who specialised in intercepting high frequency traffic of the Red Army and the NKVD^[58] The officers and men of the unit supervised the intercept traffic requirements of the KONA units and their subordinate units, directly in the case of KONA 1, 2,3,7, and 8, and through the Senior Commander of Signal Intelligence (German: Höherer Kommandeur der Nachrichtenaufklärung) (Abbr: Höh Kdr d NA) for KONA 5 and KONA 6.^[58] In October 1944, the HQ was run by Lieutenant Colonel (German: Oberstleutnant) Andrea, Chief of Staff was Colonel (German: Oberst) Köbe, with Group Z being run by Major (German: Major) Hüther.^[59]

The authority of the staff was exclusively in matters of intelligence policy and did not extend direct to intercept units in the field. It could however liaise with these through the unit staff. The final responsibility for policy, issue of intercept reports and allocation of work within the groups lay with staff HQ.^[59]

• Group (German: Gruppe) I: This unit was directed by Amtmann Bodenmüller and was responsible for two main tasks:

• The first task was the maintenance of communications between the units of the GdNA.^[59]

The signals officer of the group, Inspector Strahlendorf was in charge of a wireless centre and teleprinter centres of a network connecting to the outlying units of the HQ. Teleprinter was the preferred method of communication unit the end of the war, when radio was used. In the middle of April 1945, a plan was evolved for creating wireless stations in occupied parts of Germany for intercept purposes. Comms with these stations was to be maintained by the wireless centre of the GdNA. The plan was abandoned. Personnel employed by the comms unit were almost exclusively women.^[59]

• The second was wireless monitoring. This section was known as Radio Reception Point (German: Ic Rundfunkempfangstelle) and was commanded by Wm Pretterebner. This unit had four subsections:

• Referat Ia: The broadcast monitoring East (German: Rundfunküberwachung Ost) unit monitored eastern wireless.^[59]

Owing to personnel shortage its efforts were restricted to monitoring the Moscow wireless. Latterly, a certain amount of Balkan monitoring was instituted particularly for Turkey and Romania

• Referat Ib: The broadcast monitoring West (German: Rundfunküberwachung West) of western wireless.^[59]

Owing also to personnel shortages this unit only monitored the BBC London Service.

• Referat Ic: The Plain text monitoring (German: Helldienst) unit.^[59]

This unit was responsible for the intercept activity which concentrated on the Reuters agency.

• Referat Ic: An evaluation section.

This section was responsible for collating all information from the other three sections and consolidating it into reports. The collated reports were divided into separate parts for political, economic or military news. They were circulated within the departments of the Army High Command (OKH), sometimes with the classification TOP SECRET (German: German:Geheime Kommandosache) (Abbr. GKdos). Special news flashed on items of urgent importance were also issued.^[59][57]

• Group II: This unit which was known as End Evaluation WEST (German: Endauswertung) was commanded by Major Thiel. Formally group II was known as LNA West and was located at the Zeppelin bunker near Zossen, and had a personnel count of around 50 people, producing radio situation reports correlating the information from KONA 5, KONA 6 and KONA 7. Captain Thiel, who was head of this group, had been with the LNA for a long time, and was thoroughly familiar with the problems of western evaluation.^[57][59] The evaluation sub-section was responsible for collating all information received from the three Referat in Group I and consolidating them into reports. Collated reports were issued, divided into separate parts for political, economic or military news. The reports were circulated within various departments of the OKH. Frequently, and owing to the political nature of the information, the reports were graded GKdos (Top Secret) although they were obtained merely from monitoring enemy wireless news. Special news flashes on items of urgent importance were also issued.^[57][59]
• Group III: This unit was known as End Evaluation EAST German: Endauswertung Ost). Captain (German: Hauptmann) Gorzolla was responsible for this unit. This unit undertook evaluation of intercept traffic and cryptanalytic work emanating from the Eastern European Front, e.g. Soviet Union.

With the HQ of Group III, there was a special receiving office through which all messages emanating from the forward intercept units and fixed stations were passed. At the reception office, the unit originating the message was identified by the call signs used. Undecipherable messages were thence passed immediately to Group IV for deciphering and messages which were already in plain text were passed to the special evaluation sub-sections according to the nature of the traffic. In addition, deciphered messages were passed back from the Gruppe IV through the reception office for evaluation. The head office of Groupe III kept a central card index in which call signs, cipher indicator groups and contents of messages were registered.^[59]

The department was subdivided into the following sections:

• Referat IIIa: Traffic Sorting Office.
• Referat IIIb: Northern Sector Evaluation.
• Referat IIIc: Central Sector Evaluation.
• Referat IIId: Southern Sector Evaluation.
• Referat IIIe: People's Commissariat for Internal Affairs (NKVD) Evaluation.
• Referat IIIf: Partisan traffic evaluation.
• Referat IIIg: Swedish traffic evaluation.

Sources of information for the evaluation unit were call signs, cipher indicator groups and D/F reports. Using these it was possible to establish a detailed order of battle. Surnames were considered an exceptionally valuable source of intelligence since they were used so infrequently in Russian traffic dealing with promotion and transfer. Surnames about Major were tracked in a card index. The evaluation of NKVD traffic was equally valuable since reinforcements and movements of NKVD traffic normally indicated similar movements in the Red Army Field Army. They also gave a good indication of lines of communication. Partisan traffic was also intercepted, for appropriate countermeasures.^[59]

• Group IV: Major Rudolf Hentze was responsible for all cryptanalytic work done at GdNA. It was one of the largest groups within the GdNA, having been built up from parts of the three former agencies: The defunct OKH/Chi, LNA West at Zossen and the HLS East at Lötzen.^[59] The HLS East group, which operated in Loetzen, East Prussia, during 1942–1944, intercepted Soviet teletype transmissions. This unit was captured wholesale in May 1945 in Rosenheim, Germany, by the Allies, and transported by TICOM and put to work so their methods could be evaluated. The Allies then either directly copied the German equipment, or built similar models and used them to intercept the internal Soviet network traffic.

The unit was divided into separate Referat according to the origin of the material. Material dealt with in the Group IV, consisted of traffic which the forward intercept units had intercepted but had been unable to decipher. A certain amount of special traffic was also intercepted by the Feste attached to the GDNA.^[59]

• Referat I: The mathematician, Dr Hans Pietsch was responsible for the unit. It was responsible for analytical research. It was the former Mathematical Section of OKH/Chi. It was responsible for the security of German Army Systems.^[59]

• Referat Ia: The subsection was headed by Johannes Marquart, and was engaged in research on German Army hand cryptanalytic systems.
• Referat Ib: This subsection was managed by Dr Pietsch, handling research on German Army machine systems.

• Subsection F:This subsection designated F for the German word for research (German: Forschung). This subsection was headed by Herbert von Denffer and handled research on foreign systems.^[36] Otto Buggisch rated Herbert von Denffer as the most capable cryptanalyst within the German Armed Forces.
• Subsection 7:This subsection dealt with the security of German hand systems.
• Subsection 13:This subsection was heading by Dr S. Döring and dealt with the security of own machinery and process of German Army machine systems.

• Referat II: Headed by the mathematician Dr Alfred Kneschke, it dealt with the cryptanalysis and deciphering of non-Russian traffic. It had three sub-sections:

• Referat IIa: Cryptanalysis and decoding of British, USA and Swedish systems. This unit was managed by Dr Werner Schulze. Ludwig Falter worked as an English interpreter, mathematician and cryptanalyst on the British desk.^[60]
• Referat IIb: Cryptanalysis and decoding of French, Spanish, Portuguese, Brazilian and Swiss systems. This unit was managed by Otto Kühn. Most of the volume of traffic from these countries was extremely small and was thus was unimportant.^[61]
• Referat IIc: Cryptanalysis and decoding of Balkan systems. This unit was managed by Alfred Kneschke, previously Sonderführer Giesler, previously Oberregierungsrat Dr Rudolf Bailovic.

• Referat III: This subsection was managed by Lieutenant Alexis Dettman. The section was composed of the cryptanalytic sections of HLS Ost. It dealt with the Russian systems and had four sub-sections:

• Referat IIIa: Cryptanalysis of NKVD traffic.
• Referat IIIb: Cryptanalysis of Russian army traffic.
• Referat IIIc: Cryptanalysis of Partisan traffic.
• Referat IIId: Cryptanalysis of Russian systems.

• Referat IV: This unit was the former Hollerith machinery section of OKH/Chi. This section performed mainly statistical work. Most of the members of the unit were women used to run the machinery. The section maintained its own repair shop for the machines.
• Referat V: This unit was the training department of the GdNA where cryptographic and cryptanalytic courses were given under the direction of Inspector Kuehn, who had headed the Training section of OKH/Chi. During the last months of the war, the once flourishing section dwindled to a group of 40 students every three months.

• Group V: This unit was commanded by Amtmann Block. It had a fair wide field of activity. It had a mixed group containing three Referat all of which carried out unrelated work.^[59]

• Referat I: This section was named (German: Beutcauswertung OST) headed by Inspector Zipper, and was engaged in reconstructing Russian, British and USA call signs and call signs systems, and deducing units therefrom. It covered various procedures of enemy wireless traffic and the allocation of wave lengths.
• Referat II: This section managed specifically by Amtmann Block was responsible for the exploitation of captured Russian documents and manuals of signals interest. Captured manuals were translated and descriptions of Russian equipment examined. By April 1945, the Referat II had completed an up-to-date booklet on Russian abbreviations, which was ready for publication. This book was to have been made available to all forward intercept units.^[59]
• Referat III: This section had two tasks. The first was engaged in supplying the KONA signal intelligence regiments with the necessary intercept equipment and in maintaining a workshop to service the needs of the GdNA HQ itself.

• Group VI: This unit was located in Potsdam under Captain (German: Hauptmann) Röder, and was responsible for intercepting and evaluating special high-grade machine systems.

• Referat I, with three sub-sections, handled Russian Systems:

• Sub-Section Ia: This section was responsible for interception and evaluation of Inter-Soviet State traffic, picked up on Baudot traffic.

On the basis of this, the (German: Wehrwirtschaftsnachr) (Abbr. WWN) bulletins were compiled. These bulletins gave a detailed summary of Russian economic situation, particularly in the areas of Moscow, Baku, Rostov and included production figures and details of supply and labour conditions. About 30 copies of this report were issued. Detailed card indexes were kept, which included names and locations of factories and personalities therein.^[59]

• Sub-Section Ib: Interception and evaluation of Russian Baudot.

The unit consisted of two cryptographers who undertook research into the cipher machines employed for Baudot traffic forward of GHQ Moscow. They also assisted Referat Ic in preliminary evaluation.^[59]

• Sub-Section Ic: Interception and evaluation of Russian Army traffic.

This section picked up Inter-Soviet and Red Army Baudot traffic and dealt with the preliminary evaluation of Ref Army Baudot traffic. Based on this analysis, a situation report was brought out, giving the Order of Battle, personalities, frequencies, call signs and cipher indicator groups used in the traffic. This was passed to Group III for evaluation. Referat Ib carried out joint initial evaluation.^[59]

• Referat II had two sub-sections. Inspector Heller was responsible for this unit.

• Sub-Section IIa: Interception of western teleprinter and automatic morse traffic intercepts.
• Sub-Section IIb: Evaluation of the intercepts from section 2a.

• Group Z: This unit was responsible for general administrative control of all departments with OKH/GdNA. The work was divided into four types:

• Personnel: A central card index was kept for all personnel employed with the GdNA. The unit was also responsible for all transfers, either interdepartmental or outside the unit.
• Registry Office (German: Registratur). This communications unit registered all incoming and outgoing correspondence and was responsible for all courier communications between HT General GDNA and its outlying subordinate units. For local communications, the registry had its own runners, but for long distances, the courier services of the Army High Command (OKH) were used. In addition, the Registry Office duplicated some reports for the individual groups.
• Paymaster. All of OKH/GdNA were paid by this section.
• Drawing. This unit managed the production of situation maps and maps of WT radio networks were produced. Mimeograph and Bookbinding activity was also carried on here.^[62][59]

Russia

HLS was able during the first Russo-Finnish War to break a number of Russian 2,3 and 4-figure codes. In addition, a copy of the Russian 5-digit code was obtained, which was handed over to the Finish General Staff (Finnish radio intelligence). That particular code was used by the Russians in the first year of the war with Germany in 1939.^[46]

Netherlands

An exercise of the Dutch Army was covered in 1937. Very simple techniques, principally double transposition ciphers, were used and these could be read without much difficulty. As a result, it was possible to establish the Order of battle of the Dutch units participating in the exercise down to the battalion level.^[46]

France

Continuous and significant successes were obtained against the French (Deuxième Bureau) before the war. Before 1939, HLS Ost covered the French static wireless net which radiated from Paris to the static formations in France. Cipher procedures were continuously read, and provided valuable information during the international crisis of 1937, Spring and Summer 1938 and 1939.^[46]

Britain

Very little success was obtained in the reading of British ciphers before the war, principally due to the low quality of the personnel involved.^[46]

Static period 1939 to 1940

The signal intelligence picture provided during the early period of the war was good. The complete picture of British, French and Dutch orders of battle was available. Changes in that order could always be followed. The French, Belgium and Dutch picture was partly obtained as a result of cryptanalysis achievements, the order of battle of the British Army could only be built up by the results of Direction-Finding (abbr. D/F) information, and the evaluation of call-signs and other items of the wireless traffic procedure.^[63]

German offensive May–June 1940

France

Boris Hagelin working on a cipher machine

With the opening of the Battle of France in May 1940, the French began to use ciphers in increasing quantities. Germany at this point suffered an acute shortage of forward cryptographers and was therefore unable to undertake much work on the French forward ciphers. As a result, the forward units concentrated on the two French cipher machines, the B-211, which was an electromechanical cipher machine, designed and built by Boris Hagelin for use by the French Army and the C-36.^[30] Progress was slow, but as the result of the research on two captured C-36 machines, Army Group C was in a position by July 1940 to undertake satisfactory reading of the traffic. Likewise, it was impossible to break the B-211 machine in time for that information to be of any value. Nevertheless, the research undertaken during this period was to justify the results later.^[30]

Reorganisation of Inspectorate 7

The experience of 1940 showed that considerable expansion in the German Army cryptographic service was desirable. This organisation was carried out by Major Mang. His aim was not only to increase the cryptanalysis staff at the centre, but also to provide reserves of cryptography to work in certain key areas.^[35] The cryptanalysis section thereupon became independent and was reorganised as Group VI of In 7. Henceforth it was subordinated to the reserve army for personnel and administrative matters, but remained subordinated to Chef HNW of Field Army, just as Horchleitstelle was converted to Group IV. Nevertheless, this curious form of organisation paid, and enabled the cryptographic service to recruit sufficient personnel without serious interference.^[35] In general, the object of OKH/Chi was the organisation of cryptanalysis in the field and in the rear; training of cryptographers and the investigation of the security of German Ciphers

It was also felt that in certain critical regions, an extra cryptanalytic effort should be enforced, to help in the cryptanalysis of War Office cipher W, the British Army's universal high-grade codebook, which carried traffic between Whitehall, commands, armies, corps and later divisions.^[64][65] To this end, the Russian Referat of OKH/Chi was detached to the Horchleitstelle Lötzen, while special cryptanalysis sections for British traffic were detached to the Horch kp in the Middle East under the command of German: Oberleutnant Seebaum and Commander of Signals Troops (German: Kommandeur for Horchtruppen 4) in Athens.

Review of Central Office organisation

Prior to 1939, the Intercept Control Station [Ref 5.1] had a section for handling Russian traffic, but little was known of its operation or achievements.^[70] Early successes against Russian cryptography were evidenced by cryptanalysis of 2,3, and 4-figure codes^[63] with 5-figure codes broken at the start of the war using a Russian 5-figure code book obtained from Finland, that was used in the first year of the war.^[48] When HLS was replaced in 1941 with the new agencies: OKH/Chi and HLS [Ref 5.2], the Soviet evaluation section was moved to LNA and the cryptanalysis unit for the Soviet sector remained with Inspectorate 7/VI. In late 1941, on a recommendation by Kunibert Randewig, both cryptanalysis and evaluation sections were moved to Loetzen, East Prussia.^[48] This section formed the nucleus for the third central agency, the HLS Ost [Ref 5.5]. From that time, until 1944, the German Army Signals Intelligence activities were sharply divided into non-Russian, which were undertaken at Inspectorate 7/VI and into Russian activities, performed by HLS Ost and the LNA.

In October 1944, the three agencies were amalgamated together into the GdNA, into a central agency.^[71]

For a breakdown of Russian signals intelligence activities, Group II under Captain (German: Hauptmann) Gorzolla and Group IV under Major Rudolf Hentze were the principal units with the GdNA which worked on Russian systems [Ref 5.6.1].

Review of Field Office organisation

Introduction

Survey of Successes in Cryptanalysis at KONA 1

The Soviet Union state used various military cryptographic systems in order to secure its communication. Two organisations prepared and evaluated cipher procedures. This was the NKVD 5th Department and the Red Army's 8th Department of the main intelligence directorate GRU. The soviet military used 2,3,4, and 5-digit codes enciphered with substitution methods or with additive sequences used with the most important 4 and 5 figure codes. The NKVD relied on figure codes enciphered both with substitution and addition methods. Partisan groups also used figure codes enciphered with additive sequences or transposed based on a key word. The diplomatic service used 4-digit codebooks enciphered with One-time pads tables.

2-Digit codes

The Soviet Union 2-digit codes were used by the Russian Army, Air Force and NKVD. In the Army, they were used by Army Groups, Armies, Corps, Divisions, and Regiments; and by small independent special units such as Combat Engineer Brigades, Motor Regiments, and artillery. In the NKVD, they were used on regimental communication close to the front, and from divisional level downwards.

Cryptanalysis of 2-digit systems was done mostly in FAK units at the company level, but was also handled by NAA, the NAAS and at HQ level of the GDNA itself.

Russia 2-Digit Codes
Name of Code	Introduced	Classification	Design and Use
PT-35	Unknown	Substitution cipher	According to Alexis Dettman, who ran the Russian Referat and Sergius Samsonov who was head of Referat IIIa of Group IV, the first 2-figure operational system used over a long period by the Army and Air Force of the whole Soviet Union was PT-35, a code with 100 values, re-enciphered daily within each individual network.
PT-39 Code	Late 1939	Substitution cipher	Fig I. PT-39 Recipher table The PT-39 Code (Russian: Peregovornaa Tablica) meaning conversation table, a 2-digit code placed in a 10 x 10 square and then enciphered by substitution through a 2-digit 10 x 10 Latin square, with no figure being repeated in any row or column, and can be classified as the original, or fundamental 2-digit code.[72][73] From 1940 to 1942, it was used by Army Groups, Armies down to Divisions. The identification of the Latin square used for encipherment enabled the GDNA to establish which Russian front or army the wireless station using it belonged, or whether it was an Army or Air Force Station. Since the squares could easily be checked (which appears to have been hardly necessary, since the rows and columns could be solved) with a minimum of 15 to 20 groups. The messages were of a technical signal or tactical nature, the latter more prominent after the beginning of the Russian campaign in June, 1941. This code was used from the extreme south to the extreme north of the eastern front, and far as the Caucasus, middle Asia and North Persia.[73] Technical description The alphabet lay in three columns, the figures 1 to 0 in one column, the remainder of the square consisting of words and phrases such as CO, Chief of Staff, WT Station, We are changing to frequency. The latter groups had alternative meanings consisting of such phrases. In order to differentiate the two meanings, the first column contained two groups, one meaning Read letter and the other read words. E.g. of a 2-digit message: S.D = Rifle Division. 17 86 CO 80 37 32 56 Read Words KONA 3 6 Read Letters S D The recipher was carried out using the 10 x 10 Latin Square, i.e. no figure repeated in any one column or line. A line or column of this square was allotted to each day of the month. Ex: 7th, 12th, 19, 18 May Line A 1st, 9th, 13, 29 May Line G 3rd, 6th, 10, 19 May Column E The recipher of the bigrams 17, 86, 00, 80 on 7 May would be according to Figure I be 10, 54, 99, 59.[73]
PT-42, PT-42N	1942	Substitution cipher	Fig II. PT-42 Reciphering Table Fig III. PT-42N Recipher table PT-42 was similar to PT-39 in construction except that the distribution of values in the basic square was made random, and variants for values (as many as four for common letters such as 'o', 'e'. 'i', 'a') were introduced. The enciphering method was the same as for PT-39, but because of the random nature of value assignment in the basic square, the solution of a row (or column) of the enciphering square now required about 30 groups. PT-42 was restricted for use in Army Groups, Armies or Corps. For divisions or regiments, PT-42N was used (Fig II). It was smaller, with a square of 7 x 10 instead of 10 x 10, but its construction was the same as PT-42. As in the case of PT-42, encipherment was performed by rows, but these were rarely derived from the Latin square. It was used most exclusively from division forwards and remained in force in some cases until 1944.[73] During interrogation by TICOM, Alexis Dettman stated this code produced large amounts of tactical information. Fig. II is the reciphering table.
PT-43	1943 onwards.		The PT-42 and PT-42N were superseded by the PT-43, which was the last general purpose 2-digit code used and which remained in force up to the capitulation of Germany. Unlike the basic square in PT-39, PT-42 and PT-42N, it contained no letters. PT-43. was used for addresses, particularly by the Air Force and the Anti Aircraft Defense (PWO).[74] PT-43 came in about 1.5 years late, at which rate PT-45 would have arrived in 1946.[74]
Home-made 2-digit	Unknown		Small independent special units, such as Combat Engineer Brigades, Motor Regiments and Artillery Brigades, had their own home-made 2-figure codes, which were often in use for only short periods and which, besides the letters of the alphabet and numbers, contained specialised expressions appropriate to the unit concerned.[74]

It was clear from interrogations that 2-digit codes were not always in use, but were being constantly read. POWS of NAA 11 stated that the last known table was PT-43, and it could not be constructed.^[75] For Lieutenant Alexis Dettman, who stated that solving PT codes was:

merely a form of crossword puzzle^[76]

Dr. Wilhelm Gerlich of NAAS 1, stated that one or two men at NAAS 1 were able to cope with decipherment of 2-digit messages, especially as the greater part of them were being solved at company level. KONA 1 prisoners stated categorically that the Soviet Union has ceased using 2-digit codes after 1943,^[73] however other evidence would seem to have indicated that they were used up until the end of the war by the Red Army and NKVD, particularly by units in active combat, and were still being actively used, even if not appearing.^[77][78]

3-Digit codes

3-digit codes were used by the Red Army, the Air Force and the NKVD. They were first used in 1941–1942, initially mainly by the Air Force and later, more widely, by the Army. Traffic from Army Group down to Battalion had its own 3-digit code. The 3-digit codes were replaced by 3-digit Signal Codes in 1943, which were used by all units. For the NKVD, they were used by the Black Sea Fleet and from division downwards.

The solution of these codes was done mostly in FAK companies, but also handled by the NAA, NAAS and the HLS Ost.

They were first noticed in February, 1941, and used increasingly from May 1941 at the beginning of the Russian campaign (Eastern Front (World War II)). From then until late summer 1942, the Air Force made the most use of the code and each Air Division had its own cipher. In 1942, the 48th Army, the first Army to use it, started by using a 3-digit syballic code.

Fig IV. Example of 3-figure code book

Interrogations of personnel from Feste 10 and KONA 1: By the time of Stalingrad practically every Army engaged in the battle had its own 3-digit cipher.^[74] Dettman and Samsonov do not discuss any 3-digit codes as such, so it must be assumed that they considered these types of codes similar to the 2-digit PT series, and did not warrant discussion as a special sub-type.^[79]

Technical description

The first 3-digit ciphers were very simple in form, consisting of several pages, ten at most, and contained alphabetically semi-hatted or completely hatted, the numbers 1 to 0 and punctuation marks. See Fig IV.^[79]

Fig V. Example of 3-figure alphabetic code book

Soon afterwards the letters of the alphabet were put in their alphabetic position in the book. See Fig V.^[79]

Besides the above types of codes, syllabic codes contained few words but practically all the possible syllables which could be formed out of 2 or 3 letters. All codes of this kind which were broken were alphabetic. See Fig. VII

Fig VI. Example of 3-figure semi-alphabetic code book

After some months, the strictly alphabetic nature of the books was given up and the alphabeticity only maintained within the area of a letter. The numbers were at the same time distributed at random over the page. See Fig VI.^[79] The book could have 1000 groups, but Oberleutnant Schubert stated that the average number of groups was 300–800, stating: in general small scope, but frequent change.^[80] If the codes were smaller than 1000 groups, alternatives were given either to pages or first figures of the lines.^[81] The substitutions could be constructed without any recognizable system or they could be made up from a Latin square, with the square usually lasting about one month, although with the Air Force, it sometimes lasted longer.^[81] Schubert stated that towards the end of the war, there appeared quite isolated 4 to 7-digit substitution, presumably private systems of the respective cipher departments, but appeared very seldom.^[81]

From the beginning of 1943, most 3-digit codes no longer contained single letters but used the initial letter of the words for this purpose. In order to indicate which meaning was to be used two groups were introduced:

736 1) Read the initial letter

737 2) Read the whole word

Fig VII. Example of 3-figure syllabic code book

The 3-digit groups were read in the order of page-line. The recipher of 3-digit ciphers was as varied as in the case of 2-figure ciphers. Each figure was re-enciphered separately. This is to say, for the page numbers, a hatted order of the figures 1 to 0 was substituted. Thus Page 1 became 4, 2 became 6 and so on. Fig. VIII.^[82]

3-digit code R3ZC which was mentioned by Corporal A. Faure of NAA 11 and was discovered as part of the Norway codes.^[83] It was a code with 10 pages of 100 positions each, 10 x 10 alphabetically arranged. One column of each page, the 8th was empty. Only the 100's and 10's figures of each group were reciphered.^[83]

The 3-figure code, it is clear from all interrogations, was mainly used by the Army, but also by the Air Forces. According to a report by Uffz. Karrenberg of Group VI, on regimental networks and for less important messages on the level of assault armies, mainly the 3-digit codes (with a 2-digit Latin square encipherment) was used.^[84] KONA 1 personnel stated that every Army Group down to Battalion had its own 3-digit code.^[82]

It is curious to note that a good deal of plaintext was inserted into the 3-digit enciphered code as it was transmitted.^[80] Gerlich pointed out the advantages of plaintext insertion stating: They often gave words and names not contained in the code. 3-figure traffic was always solved when one encipherment was available^[85] 3-figure traffic was only slightly more secure that 2-digit code traffic and was 80% readable.^[86] It was known that Air Force codes were often current for much longer periods than those for the Army, and thus be able to find depth. Army 3-digit codes were changed after a big operation and were in use for one week to one month. However, all 3-digit codes were readable^[87] and Lt. Col. Mettig stated that from spring 1943 to 1945, 2-digit and 3-digit traffic was read regularly, providing a large amount of tactical intelligence.^[48]

The operational 3-digit codes were discontinued in 1943 and replaced by 3-digit Signal Codes, which were different only in that they contained no letters, only words and phrases of importance, and were not alphabetic but had meanings grouped under headings such as attack, defend, enemy movements. Each meaning had two or three, 3-figure groups allotted to it. As in the case of the former code, anything not in the codebook was sent in plaintext.^[82] It was assumed that these types of codes were also read as consistently and as fully as the 2-digit and 3-digit codes they superseded.

4-Digit codes

4-digit (abbr. 4/F) codes were used by the Army, Air Force and NKVD. There were used in the Army as General Army Codes, called General Commanders Codes, and on lower operational levels by mobile formations such as Tank and Mechanised Corps, Tank Armies, and Tank Administration and Supply Units. For the NKVD, they were used on Railway and Transport Nets.

Solutions to these codes were handled at FAK, NAA and GDNA level. At FAK level, the companies usually had a 4-figure unit, as well as a 2-digit unit and 3-digit units, in a cryptanalysis department.^[88]

Lt. Schubert of KONA 6 stated under interrogation that: The Soviet Army keys are 3 or 4-digit systems. The basis is the same.^[80] The construction of 4-digit codes was the same as 3-digit codes, except the book had a possible 10,000 groups instead of 1,000.^[82] with the book length being described as either six or seven pages^[80] each with a block of consecutive numbers, or with KONA 1 personnel stating that book length being of from 5 to 100 pages long. The latter value seemed more likely.^[89] The Air Force Codes usually had about 10,000 groups and the Army 5,000 groups, and each page could have a variant page designation.^[89]

5-Digit codes

5-digit codes were used by the Army, Air Force and NKVD. In the Army, they were used by the People's Commissariat for Defence (Russian: Narodny Komissariat Oborony), Army Groups, Armies, Corps, Divisions and Brigades. In the Air Force, they were used by Air Armies, Air Corps, Air Divisions, Regional Air Bases, Anti-Aircraft Corps and Divisions and Anti-Aircraft units. They contained strategic, tactical, personnel and supply matters, and political reports and directives.

With the exception of a short period in 1943, when KONA 1 did independent 5-digit cryptanalysis, solution of 5-digit codes was handled exclusively by the GDNA.

In discussing the achievements of the OKH/Chi, Lt. Col. Mettig, stated glibly:

The breaking of the Russian 5-digit reciphered code...was the most outstanding cryptanalytic achievement of In 7/VI.

The Soviet 5-digit code was broken chiefly by War Administration Inspector (German: Kriegsverwaltungsinspektor) Lieutenant Alexis Dettman.^[99] When rating the relative importance of cryptographic including cryptanalysis achievements contributing to total intelligence, Mettig was most impressed by the continuous breaking of the Russian 5-digit code despite the difficulties that were experienced after spring-summer 1943.^[100] However Mettig could have been stressing organisational changes carried out to facilitate the breaking of codes rather than actual cryptographic achievements. Dr Otto Buggisch, also of OKH/Chi stated that Mettig had few fundamental ideas of cryptanalysis.

Certainly other evidence exists that points conclusively and without doubt to an almost complete failure on the part of the German cryptanalysts to make any progress with the solution of the 5-digit code. Corporal (German: uffz) A. Althans of the KONA 1 stated that cryptanalysis of 5-digit codes was only possible with the following conditions:

• There was a number of messages, at least three, which had the same additive applied.
• The 5-digit code had been captured.^[101]

Dettmann and Samsonov^[102] stated that codes 011-A, 023-A, O45-A, 062-A and 091-A used successively from the beginning of World War II to the end, did prove difficult from a pure cryptanalytic solution. They stated:

It is interesting to point out that during the course of the war all the newly appearing versions of each cipher were captured through fortunate circumstances and always so soon that the originals were almost always in the hands of the cryptanalysts at the instance of their being put into use by the Soviets.^[102] Of course, this 'contentious capture' was an aid in solution, under such circumstances because of the One-time pad encipherment. The individual tables offer almost complete security against breaking.^[103]

In the reports of personnel from NAA 11, a Captain Schmidt stated that:

With regard to Russian [Soviet] traffic, the Abteilung [Battalion] did everything up to and including 4-digit. 5-digit they considered insoluble and forward these to the GdNA.^[104]

One Corporal Karrenberg, of GdNA, while under interrogation discussed 5-letter and 5-digit codes used for operational orders, stated:

These were so-called Blocknot codes, which were only used once and were therefore unbreakable.^[105]

Blocknots were random sequences of numbers contained in a book and organised by numbered rows and columns and were used as additives in reciphering and were considered as a type of One-time pad. The GdNA mathematician Johannes Marquart conducted research on Blocknots and was unable to determine how they were generated. Corporal Karrenberg stated flatly:

5-figure and 5-digit messages were not touched at all. In general very little work was done on decipherment of 5-group messages, although these contained the most important operation reports. They were only used to identify units and were only read if code books happened to have been captured.^[106][86]

In 1943, KONA 1, for a period, undertook 5-digit cryptanalysis independently of GdNA,^[101] but the general practice was for all units to forward 5-digit traffic directly to Berlin to GdNA for possible cryptanalysis and evaluation. Karrenberg stated:

even at the GdNA HQ, very little attention was give to 5-digit messages and very little enthusiasm displayed in working on it. Only the preambles were used to identify units, from Blocknots and indicator groups.^[107]

Finally Lt. Schubert, when questioned on possible success on 5-digit codes replied:

In the Finnish campaign the book was captured and the Russians used the one-time pads over again. Because of this we had considerable success. Recently the Russians used the [one time] pads correctly and only very few messages were read, these through re-encodements.^[98]

Address codes

Soviet Address Codes (2-digit, 3-digit, 4-digit) were used by the Army for Army Groups, Armies and Independent Corps. They were used more widely by the Air Force and the Anti-Aircraft Defense.

Solution of address codes was considered somewhat special to judge the statements in KONA 1 interrogations describing cryptanalytic operations of the various units:

Unit numbers by signal organisation
Unit Name	Comment
In the FAK	15 to 20 people were adequate for company cryptanalysis. Special procedures such as Signal Codes (3-figure and 4-figure) and word codes and address codes (3-digit) were studied by chosen cryptanalysts.[109] The strength of the various sections was modified to cope with developments on the Russian side: namely the shifting of emphasis from 2-digit to 3-digit and then to 4-digit traffic. Special procedures, such as Signal Codes (3-digit and 4-digit), Word Codes and Address Codes (3-digits), were studied in the appropriate section by specially chosen cryptanalysts, for the most, also sometimes by the chief cryptanalyst. The average working time to recover a new code varied a great deal and depended on the difficulty of the procedure.[109]
In the NAAS	Section 4 of the NAAS, concerned with new developments in cipher design did the real cryptanalysis. It normally concentrated on difficult systems which the companies had neither the time nor manpower to deal with adequately. It consisted mainly of mathematicians and worked on ~ inter alia, addresses, specifically 2-F, 3-F and 4-F address codes.[110]

Although mention was in the KONA 1 interrogations of 2-digit address material, nothing was recorded in the interrogations on this subject except one statement in the final interrogation of NAA 11 personnel:

Bigrams and Trigrams in Addresses. Blome knew of the two used separately, but could not recall any case of the two in conjunction. He suggested that this might accompany something he had seen, namely 3 Z code mixed with 2Z traffic.^[75]

There was no record of extent or success of solution with regard to 2-F address codes. Likewise, there was no description of 4-F (figure, or digit, both the same) address codes nor any statement regarding the extent or success of solution.

Oberleutnant Schubert of KONA 6, stated that towards the close of hostilities, the Soviets (Russians) were using 3-F codes for addresses. He stated:

In this code the clear position remained unchanged for periods, but the ciphers were changed daily. These ciphers were in some way related to the call signs.^[111]

The only description of 3-F address codes was given in the KONA 1 reports.^[112]

Technical description

Fig X. Example of 3-figure Address Code

3-Figure (3-Digit, or 3-F) Address codes were used in conjunction with 5-Digit messages to enable wireless stations to ensure that messages arrived at their proper destination. Their construction was similar to that of the PT-39 or PT-42 codes,^[113] described above, but they contained only figures, unit designations, authorities, words such as for or from.^[114] See Fig X.

Example of an address:

783	625	825	824	017	389	930	837	401
For	Cipher Branch	5th	Army	from	4	Guards	Tanks	Corps

A code of this type was first used at the beginning of 1944^[115] on the 1st and 2nd Ukrainian and the 1st White Russian Fronts for communications between their Army Groups and their respective Armies and independent Corps. In the summer of 1944 armies began to use similar codes with their subordinates units and latterly the use of such codes increased still further.^[114]

The solution to these codes, given a fair amount of material, was generally easy. They were often simpler than the example given in Fig. X and sometimes appeared in the form of straightforward lists with each meaning numbered consecutively of 100 pages instead of 10.^[114] See Fig XI.

The same variations in construction occur as with three-figure.

• Alphabetic with the letters of the alphabet grouped at the end of the Code.
• Each letter of the alphabet placed before the part devoted to words beginning with that letter.
• Semi-hatted, i.e. with all the words beginning with one letter grouped together but the groups in random order.
• Letters of the alphabet with alternatives.
• Syllabic Codes (with words distributed over the code).
• Letters of the alphabet with alternatives.

• Read the initial letter.
• Read the word.

• With the two groups directly above appearing several times, often on each page.

Codes had anything from 5 to 100 pages. The Air Force Codes usually had about 10,000 groups and the Army 5000 or fewer. According to members of KONA 1, the solution of these codes given a fair amount of material, was generally easy.^[82] Members of the NAA 11 stated the following:

Addresses to personal names rather than titles were common in all Russian traffic and this suggested the use of initials. The vagueness of this answer surprised the interrogator who asked if the addresses, being enciphered on the PT table, were not read currently. The answer was that unless the same address was used frequently and some outside hint was given they were unusually unable to read the address. They supposed it used values which had special local meanings added to the table.^[75]

Miscellaneous codes

Most of the statements given here are taken from the interrogations of members of KONA 1. It is not the complete story, as the POW's themselves were aware:

The examples described are only those ciphers whose basic construction was established. There were many types of cipher which were only partially broken (solved) and whose basic form could not be established, these are not mentioned.. The number of Russian ciphers of all types that were broken was about 3000.^[116]

4-letter codes

4-Letter Transposition cipher table. Fig XVI

Two forms of four-letter codes first appeared in practice traffic between Army Groups and Armies and Independent Corps of the 1st Ukrainian Front in November 1944:

• Revolving Stencil

This consisted of a sheet of paper ruled off into 8 x 8 squares. On top was placed another sheet in which 16 holes were cut of corresponding size to the squares on the first sheet. These holes were so cut that if the sheet is turned through 90° round the centre point in the four possible positions and a letter written on the bottom sheet through each hole in each position, all 64 squares on the bottom sheet would be filled. The text of the message to be enciphered was written in the holes horizontally with the stencil in the first then in the second, third and fourth positions The cipher text was then read off horizontally and sent in four letter groups. If a message was longer that 64 letters the process was repeated as many times as necessary. The revolving stencil was changed from time to time.

• Transposition

This cipher is a simple transposition cipher, the key given by a Keyword and the text being written in vertically according to the key and either upwards or downwards according to accompanying instructions. The cipher text was then read off horizontally and sent in 4 or 5-letter groups. See Fig. XVI

The contents of messages sent in both the above types of cipher were usually about technical signal matters though in later stages units and positions were named.

Word-Code

Example of Word code. Fig XVII

From the middle of 1944, a word code was used in the area of the 2nd Ukrainian Front. The book consisted of two halves, each designated by a word such as SEVER ZAPAD literally meaning North West. Clear groups such as numbers, units, offices, designations such as Tank, Guards, Mechanised, were grouped in two columns. Each half of the code identified was only used by the Army and contained strategic and tactical reports and the names of the units. They were small in size and contained only essential groups.^[117]

The first half of the code is used with column 1 and the second half with column 2. The order of the halves can be changed and indicated by the indicating word.

If the cleargroup consists of more than one word such as In the former sector = Dolvnost and the wanted word is former, this can be indicated by saying the second word of DOLVNOST. See Fig XVII.

Example:

MOLIĀ	POZDNO	REMONT	KTO	PAKET
1a	3	Guards	Tank	Army

The codes identified were only used by the Army and contained strategic and tactical reports and the names of units. They were small in size and contained only essential groups. Anything that could not be enciphered was sent in plaintext or in the clear. Coordinates also appeared in messages.^[116]

NKVD codes

NKVD Codes were simple mono-alphabetic Substitution cipher 2-figure, 3-figure, 4-figure, 5-figure and 5-letter types. They were used without any apparent reason on two large networks:

• The networks of the NKVD Central Authorities, that were divided into those of Security Troops, Frontier Troops, and Railway Troops and Convoy Troops.
• The network of NKVD Formation, communication between units attached to Army Front Staffs.

4-figure and 5-figure codes were used on the front line: there was a 4-figure code, e.g. used by the military police, and a general 4-figure code used on Staff-Regiment-Battalion links.

Solution of NKVD codes was handled by the NAAS and the GdNA. In interrogation:

The traffic of the NKVD formed a special group of Russian wireless traffic. The distinction applied equally to the manner of conducting traffic and to the message themselves.^[129]

The German Army cryptanalysts reflected this Russian distinction in their own attacks on NKVD systems, allocating the work, again in their own attacks on NKVD systems, to levels of operation determined by difficulty of solution. Lt Ed. Wöllner of KONA 1, stated that:

NKVD traffic was always covered, but only by FAK companies. Evaluation and cryptanalysis were done by NAAS.^[130]

On the same subject Lt. Löffler of Feste 10 stated that

all NKVD signals originated in the regiments area were worked on in the NAAS, others were sent to the LNA.^[131]

But in neither case was there specified what type of NKVD traffic was worked on, and what type was passed to higher echelons. Apparently the distinction corresponded to that observed in the case of actual army traffic. All lower-level operational codes, up to 4-figure codes, could be handled by the NAAS. The 5-figure codes were not dealt with by the KONA, but handled by 40 to 50 men in the LNA, [Ref 5.4] at Zeppelin bunker at Zossen.^[132] Löffler thought that a good deal of success was obtained in the case of Far Eastern Traffic. An additive was used for the recipher.^[132] Dettman and Samsonov substantiated this point, in their discussion of the German army cryptanalytic effort:^[133]

All the five-place message material from the Army or the Airforce, as well as the NKVD messages, was submitted for the exclusive processing of the GdNA

They also gave full descriptions of NKVD systems.^[134] There was no discrepancy between the facts in their report and the facts given by Lt. Löffler. The details of description were scattered throughout the report according to types of encipherment. They mentioned the following:

• Mono-alphabetic substitution systems common to all NKVD organisations.
• Conversion systems: substitution and additive:

• 1936: 4-figure code: 2500 values, used in district.
• By 1939: three 4-figure conversion systems with codebooks of up to 5000 values, enciphered by digraphic substitution or conversion table.
• 1939: first general NKVD 4-figure code, with 10000 book positions enciphered first by single digit substitution, later by additive. At time of capitulation, three 4-figure systems (ZERNO, NEVA, VIZA, see infra) used respectively by:

• NKVD Troops.
• NKVD Border defense troops.
• NKVD Security troops.

(200 messages were read daily in all three)^[135]

• 5 figure Railway Troops code, which used 2500 groups with digraphic substitution encipherment. A few 3-figure small codes (read currently) existed, that used letter transposition. These were never found in NKVD traffic number series.

• 1940: 4-figure single letter conversion encipherment (1941–1942): 4-figure, enciphered by text key, which was letters equalling numbers.
• 1942: 4-figure enciphered by military technical manual (used by Interior troops) until end of 1944 with encipherment combining single digit conversion and Gama Tables (no description of these is given).

NKVD codes technical description

NKVD traffic was always covered, but only by Long Range Signals companies, with evaluation and cryptanalysis done by the NAAS units.^[130]

When W/T traffic was restricted during radio silences, NKVD traffic was often the most important source for Radio Intelligence. At such times, it was more completely covered. When the Army W/T was in full swing, coverage of NKVD was correspondingly reduced. On an average day, 6–12 receivers were employed exclusively on NKVD cover.^[130]

In general the following nets were covered:

• Networks of Central Authority. The covered the Chief NKVD authority in Moscow with the Front HQ's. The NKVD W/T radio intelligence picture, gave indications of groups, or the insertion of new Fronts. E.g. the appearance of a new W/T station communication with the 1st Ukrainian Front and 2nd Ukrainian Front showed that the 4th Ukrainian Front had been inserted between the 1st and 2nd Fronts. In addition, the new Front HQ could be located by Direction finding (abbr D/F).^[130]

The Central Authority Networks were subdivided into;

• Central Authority of the Security Troops.
• Central Authority of the Frontier Troops.
• Central Authority of the Security Troops (Divisions and Brigades of the Back Area).
• Central Authority of the Railway Troops.

• Networks of Formation. This covered the Front staffs with the Grenztruppen Regiments. Communication between commanders of the security troops at the front and their regiments, was monitored. D/Fing of the Regiments revealed the approximate extent of the Front. D/F of the Chief of Security Troops with the Front HQ. Finding the High Command indicated the approximate location of the Front HQ. Besides, when a forward echelon of the Chief of Security with the Front HQ appeared, it was possible to deduce that the Front HQ would move. This, on the basis of NKVD traffic alone.^[130]
• Regiments to Battalions. Most of the messages could be read, they mentioned Army units by name, e.g.;

• Before the attack from the NEISSE sector (1st Ukrainian Front), a 2nd Army and 3rd and 4th Field Replacement Rifle Regiments were mentioned by III Bn.of the 83rd Grenztruppen Regiment, operating in the Görlitz area. The conclusion drawn was that the 2nd Polish Army had been newly brought up to the NEISSE sector.^[130]
• Lines of advance and boundaries of battalions were mentioned. Battalion boundaries often proved to be Army boundaries.^[130]

Traffic of rear NKVD troops and of the Signals Regiment were of no interest, and were not covered by KONA 1.^[130]

A constant watch was kept on the 1st network, Central Authority of the Security Troops. It consisted of the communications between the Central NKVD Authority in Moscow and the commanders of those troops in Army Groups, directing staffs North and South, the less interesting GHQ Signals Regiments. These messages were not readable.^[129]

Apart from the characteristics already noted they were also to be recognised by their use of Call-signs which were made up from a square.^[129] The Russian wireless station numbers were:

Wireless radio stations
Station numbers		W/T Radio station name
	08-12	Central Authority Moscow
23	08-12	Central 3rd White Russian Front
24	08-12	Central 2nd Baltic Front
25	08-12	Central 1st White Russian Front
26	08-12	Central 1st Ukraine Front
27	08-12	Central 3rd Ukraine Front
28		Higher directing staff in Lodz
29		Front staff 4th Ukrainian Front
49–65	1-17	Independent GHQ. Signals Regiments
81		Directing staff north (Minsk)
84		Front staff 2nd Ukrainian Front
85		Directing staff south
87		Higher directing staff, area east of Stanislaw
60		Unidentified

The method of working was controlled (German: Kreise) circle working. The Kreise were known by the number of the controlling station. They were:^[129]

• Kreis VIII: Station 8 with 21, 23, 23 Night Frequency on 3170/3380 kcs
• Kreis IX: Station 9 with 20,21,25,28 Night Freq. on 3850/4230 kcs.
• Kreis XI: Station 11 with 26,29,87 Night Freq. on 4580/4940 Day Freq. 7400/8670 kcs.
• Kreis XII: Station 12 with 27,84 Night Freq. on 4580/4940 kcs.
• Kreiss LXXXI: Station 81 with 20,21,22,23,24,25,28,49,50,55,57,59,60,61,63,65 Night Freq. 2850/2975 kcs. Day Freq. 4080/4480 kcs.
• Kreiss LXXXV: Station 85 with 26,27,29,51,52,53,54,56,58,62,64,80.84,87 Night Freq. 2700/3050 kcs. Day Freq. 3950/4400 kcs.

Call signs were mostly pronounceable. The Front Staff networks usually changed their call-signs daily, the Regiment networks at regular intervals of several days, in many cases of weeks. Frequencies used lay mainly between 2400 & 3600 kcs. It should be mentioned that 5-figure NKVD messages had been picked up in nets identified as belonging to the Army or the Air Force, such messages contained SMERSH in the preamble. Such messages were originated by units of the Red Army counter-intelligence units.^[130]

Lt. Schubert spoke of two 5-figure codes, the SMERSH organisation code, used with an individual subtractor, and the Railways Troop codes, that was a 4-figure code, enciphered with substitutions tables, the 5th digit representing the quadrant on the page in which the group appeared.^[136][137] Schubert was more familiar with the 4-figure NKVD codes, which were apparently more exploitable than the 5-F codes.

The Security Troops Codes were of two types. One was used forward of regiment, when a regiment was used in approximately an Army Group Sector, i.e., it is a cipher, therefore, used forward of Army Group.^[138] This particular code ran for comparatively long periods, at least 1.5 years. The code, a Substitution cipher, was alphabetical and contained 100 pages, with 25 or 50 groups per page, and enciphered by means of an enciphered indicator, which provided for page and position substitution, the result of which was again enciphered by a substitution table. These substitution tables were also valid for a longer time and varied with the network.^[138] The additives on the page did not change, only the substitution table.

The second type, a code used rearwards of regiment, was enciphered by a figure subtractor originally from tables (up to September 1944). The same tables could appear on different networks, and since the subtractor was used very frequently, it was not uncommon for 20 messages to have the same subtractor^[138] In October 1945, 2 subtractors were used, taken from different tables, and the indicators for the 2nd subtractor were enciphered with the first one.^[136] In spite of the potential difficulties involved in this method on encipherment, the system was solved by 15 February 1945, though mainly because of bad Russian usage of the system.

The Frontier Troops Code was exactly like the Security Code rearwards of regiment, with a different basic book, at least in traffic out of Saint Petersburg (Leningrad)^[136] Lt Schubert made a statement on the Railways and Convoy Troops code quotes above.

The 4-F NKVD codes exploited by KONA 1 were used by front line units, i.e. regiments and battalions, mainly employed by the Soviet Military Police. From the period of 1933 to 1942, code R4ZC4 Russian 4-Figure, Code 4/ was in use. It consisted of a 100-page alphabetic book each with a hundred lines. It was broken by Germany in 1940.^[139] Only one code book, known to Germany as R4ZC 1800 and to the Russians as KODOWA TABLICA ZERNO was used by the NKVD from October 1943 until the end of 1944.^[132]

NKVD R4 Z C 1800 Code

Bigram substitution table for R4ZC1800

Pagination table for R4ZC1800

The R4 Z C 1800 code, had since October 1943 had 50 pages, each consisting of 50 lines and totalling 2,500 clear groups, alphabetically arranged. Each page is shifted by means of Cipher square (German: Chiffranten) and the bigrams (ab and cd) are then replaced by others according to a substitution table.^[140]

The recipher consists of two elements:

Shifting by means of Chiffranten enciphering: Any figure, chosen from Row A (sample code in Annexe 1), will indicate on any page, in Row B below, the figure must be added to that standing beside the clear group (and subtracted when deciphering).^[140] The chiffrant consisted of the figures 0 to 9 in random order printed at the top of the page, a different order being used for each page. The third figure of the 4-figure indicator group gave the number of the chiffrant to be used, i.e., if 5 was the 3rd figure of the indicator group, the fifth figure of the chiffrant reading from left to right would be the one used for each page. This number was then added to the numbers of the lines on the page before they were reciphered by means of the bigram table, i.e. if the number was 6 then line 00 would become 06 and line 24 would become line 05.^[132]

Substitution of bigrams: For the first and second halves of the 4-figure group (elements ab and cd) there are substitution tables, each of which contains 100 bigrams (each bigram from 01 to 50 occurs twice). There are 10 such tables (numbered for the most part from 0 to 9).^[140] Two different bigram substitution tables were used for reciphering the big ram representing the page and that representing the line. 10 such tables were in use concurrently for the recipher of both page and line. Each table was 10 x 10 so that each bigram could be reciphered in two different ways and each table was designated by one of the figures from 0 to 9. The figure designating the table used for the line was put in the second place of the indicator group and that designating the table used for the page in the fourth place. The first place was a dummy. A series of substitution tables was current for a period of from 2 to 6 months.^[132]

The reciphering is indicated by a 4-figure group (indicator) which appears at a definite position in the message and contains;

• Number of the clear-group table (indicated with two digits).
• Chiffrant.
• Number of the pagination table.

Example:

Indicator 0151

Chigruppe 2406

Decipherment (according to the tables below)

Element ab (=24) yields 20 according to the pagination table. The clear-group therefore is on page 20. Element cd yields 02 according to the clear-group table. From this the chiffrant is subtracted, in this case 1 (the number of page 20 under the fixed figure 5). Thus the clear group 2001, which represents Komandirowatj is derived.^[140]

The indicator group was inserted en clair in one of the first ten groups of the message according to instructions. The penultimate group consisted of the date and length of the message and the last group the Chi number.^[132]

R4ZC4 was used from 1933, solved in 1940 and in use until 1942. There were 100 pages each with 100 clear groups arranged alphabetically. Recipherment was by means of 31 substitution tables.

NKVD Other codes

Though the emphasis by the POW's being interrogated by TICOM was on 4-figure NKVD codes, it should be pointed out that a great variety of encipherments were worked on, though not all of them read. Corporal Karrenberg, gave the following breakdown of nets and types of codes used:

• Administration networks: usually sent 5-figure messages and less often, 4-figure and 5-letter messages.
• Frontier networks: used 4 and 5-figure codes: on regimental networks, also 2-figure systems.
• Black Sea Fleet: used 3-figure and 5-figure codes networks from divisional level downward: used 2-figure and 3-figure, plain language and figure messages with plain language.^[141]

Corporal Exeter of NAA 11^[142] stated that he worked on 2-figure NKVD codes. Traffic of an NKVD net on the White Sea Front, controlled from the NKVD HQ at Archangel was worked on with some success.^[142]

NKVD Conclusions

In general, certain elements seemed to be constant in all NKVD codes:

• Simply that NKVD messages were enciphered on the same system.^[143]
• NKVD messages were always arranged alphabetically.^[144]
• NKVD messages whether 5-letter or 4-figure or 5-figure, had the date in the penultimate group.^[145][139]

German Army Cryptanalytic Effort 1939-1941

In the early years of the war, the cryptanalytic staff of the Horchleitstelle [Ref 5.1] were unable to cope with the added burden of the wartime traffic. The British section of the HLS was unable to solve British systems.^[30] The failure of the British section of the Horchleitstelle to achieve any success with British ciphers and codes continued. In 1940, the six people comprising the section were moved to Bad Godesberg where no successes were achieved despite an abundance of material with which to work on.^[30] Dr Otto Buggisch who, in 1942, looked over the files of the British section regarding work on the British high grade machine, Typex, characterised the work of Inspector Breede who worked in the winter of 1939–1940 on the British "big machine" as complete nonsense.^[30] Buggisch stated that Breede described an imaginary machine which had nothing whatever to do with Typex. No cryptanalytic success was recorded in this period. In April 1940, however, the British section received a copy of the British War Office Code captured in Bergen during the Norwegian Campaign. A second copy was obtained at Dunkirk.^[160] Successes with this system were therefore possible, since the British continued to use this system until 1943.^[161]

The failure of the cryptanalysts of the Horchleitstelle to solve independently the French Army succeeding the F110 was another indication of their inadequacy. In early autumn 1939, the French replaced the peacetime ciphers, the F90 and F110 cipher with a new wartime cipher whose names was not known to TICOM sources.^[162] The French section was forced to call upon the services of the Cipher Department of the High Command of the Wehrmacht (OKW/Chi) to aid in the solution of French Army systems.^[162] Dr Erich Hüttenhain was sent to the Army Intercept Station in Frankfurt to aid in the solution. Among his papers were two memoranda, where Hüttenhain reported that the task was accomplished with his own colleagues at OKW/Chi by October 1939. Among those who worked with Hüttenhain, when on 2 September 1939, the old French Army F110 code was changed was Professor Ludwig Föppl of HLS with Trappe and Schmidt of OKW/Chi.^[162] There were not enough cryptanalysts on HLS to furnish the forward units with adequate staffs.^[30] The system worked so successfully that all the September material could be read retrospectively. The system continued to be worked on successfully through to November. Hüttenhain returned to his own agency with the system solved. It may be noted that the head of the Army station requested of Hüttenhain to convey the thanks of the army to OKW/Chi for the assistance given to HLS's section and remarked that in his opinion such a large cryptographic task could not be done by the Army Command either then or in the near future.

The system was solved until the German offensive in the spring of 1940. At this time, the French began to use systems in forward echelons which Horchleitstelle was unable to solve.^[30] Mettig remarked that the Army cryptanalysts both of the forward units and the HLS finally concentrated on two machine systems, the C-36 cipher machine and the B-211.^[30] Neither was solved however, until after the Armistice of 22 June 1940 and a considerable quantity of captured documents. According to Mettig, the final solution of these two machines rated lower than that of the preceding system since it was not timely and was done only with the aid of captured material.^[100]

In the winter of 1939, the dearth of field cryptanalysts became apparent to the German Army. When the Kommandeur der Nachrichtenaufklärung (KONA) signal intelligence regiments were preparing to move into the field, the army found that there were no trained cryptanalyst personnel to send with them.^[30] Colonel Kunibert Randewig, the commander of all intercept units in the west, was able to procure cryptographers for intercept units around Berlin and filled out that number with mathematicians and linguists.

German Army Cryptanalytic effort 1941-1945

Western and Southwestern Cryptanalysis 1941-1944

Western and southwestern cryptanalysis was handled at In 7/VI by British section with outposts in North Africa, Athens, Paris and Bergen, Norway. The American and the French section with subsections for the Swiss, Spanish, Portuguese and Brazilian traffic. The Italian section was within this group. The field units which handled western and southwestern traffic were the western field units, KONA 5 and KONA 7. The Swedish Army traffic was handled by a special unit of Feste 9 in Norway.

Work on British traffic 1941-1944

Work on USA Traffic 1941-1944

The USA section of In 7/VI was created with the entry of the United States into the war in early December 1941.^[49] The section, made up of personnel who had been drafted from the mathematical section of OKH/Chi, was placed under the leadership of Friedrich Steinberg, a leading mathematician. Initial attempts at breaking USA traffic was fraught with difficulties. Due to the size of the US wireless network and the use of alternative frequencies by USA operators, considerable trouble was experienced in identifying the various links and sorting the different systems. After a few weeks however, order was established through the reading of Call signs and the sorting of discriminants.^[49]

The first major success of the US section was in the summer of 1942 when the M-94 device was solved.^[184] In 7 designated the M-94 unit, either URSAL, CDAF, strip and ACr2. URSAL was given to the system from the fact that traffic from the US weather stations in Greenland which used URSAL as an indicator provided the first breaks into the system.^[185] CDAF was found in the traffic emanating from the Caribbean Defense Area.^[186] Strip and ACr2 (German: Amerikanischer Caesar 2) stem from the fact that this system was long thought to be a strip system.^[185] The solution of the M-94 was achieved by Friedrich Steinberg and Hans-Peter Luzius, mathematicians of the US section, who are said to have written a 25-page report on their work. After the cryptanalytic solution was achieved, a USA manual (FM 11–5) with a complete description of the M-94 was found in a Berlin library^[185]

Current solution of the M-94 from 1942 to 1943 was done both at OKH/Chi and at KONA 5 at St. Germanin. The work consisted of finding the daily key. A set of 25 charts of synoptic tables, corresponding to the 25 discs of the machine was constructed, apparently similar to the synoptic tables used by American cryptanalysts. The daily key was found by assuming a beginning, and using the charts to discover possible disc arrangements. Later, IBM machinery was used to eliminate impossible charts. Graupe of NAAS 5 stated that it usually took two days to recover the order of the discs and that only fifty groups were required for the system to be broken.^[186][173] Estimates on the amount of material solved range from 70% to 90%.

The M-94 was succeeded in 1943 by the M-209, which was first solved by the Germans in the autumn of 1943,^[187][173] and continued to be solved with some success throughout the remaining years of the war. The breaking of M-209 was achieved in OKH/Chi by Steinberg and Luzius, who were aided by the knowledge that the US government had brought the Hagelin machine which had once been offered to the German government.^[174] At first only relative settings could be recovered,^[173][188] but later the section refined its technique of recovering absolute settings so that not only paired messages but in a large number of cases, a whole day's traffic could be read. The technique of achieving true settings was passed on by OKH/Chi to the Kriegsmarine and the Luftwaffe.^[189]

Work on an operational level was carried out jointly by the US section of OKH/Chi and NAAS 5 at St. Germain. Early in 1944, NAAS 4 had been supplied with a group of cryptanalysts skilled in work on the M-209, and this small group competed with the section at In 7/VI in the quick solution of M-209 traffic.^[185] It estimated that 10%-20% of all M-209 messages intercepted were read by establishing the true settings of the wheels, and that about half of these settings were established at OKH/Chi, half at NAAS 5.^[190] To insure speedy solution all subordinated to KONA 5 were ordered to teleprint to NAAS 5 all messages on the same settings or with Indicators differing only in the first two letters.^[191] Under the most favourable circumstances two days were needed to solve a depth, and two more days to reconstruct the absolute settings.^[192] There were times, however, when captured lists of keys or settings made possible a quick solution of the traffic. During the Allied invasion of Sicily and the Allied invasion of Italy, messages of great tactical value were decoded using captured booklets containing M-209 settings.^[187][190] At the time of the Normandy landings, the M-209 keys of the 82nd Airborne Division and 101st Airborne Division which covered the critical days of 6–11 June were captured and all traffic on those days was read.^[190]

In 7/VI knew of the existence of a big American machine which was designated the AM1 (German: Amerikanische Maschine 1), but it was clear that OKH/Chi never solved this machine and had no idea about its construction.^[193] Hentze stated that his unit (KONA 5) never succeeded in getting a model of the machine.^[166] Other statements by OKH/ChiI that the machine was tackled in Berlin was considered utter nonsense^[194]

OKH/Chi were successful with American codes. The Army Administrative Code, designated by In 7/VI as AC 1 (German: Amerikanischer Code 1) had been captured before 1939, and photostatic copies of the code had been distributed to all field cryptanalytic units.^[193][195] The code was a 5-letter code with 60,000 groups, each page containing 90 groups.^[176] Feste 9, intercepted and read traffic from this code from the summer of 1942 to the autumn of 1943, while stationed in Bergen, Norway.^[176] Although no traffic of strategic value was passed, the intelligence was valuable enough so that when AC 1 was succeeded by a simplified version designated as TELWA, Feste 9 reconstructed the code.

Feste 9, aided by the US section of OKH/Chi, also broke the simple codes used by the US Army units stationed in Iceland and the Caribbean. These were designated as Divisional Field Code (DFC) followed by a number indicating the variation of the system. The variations described in TICOM sources were: DFC 15, 16, 17, 21, 25, 28, 29.^[176][196]

Mention should also be made of the success of the US section of OKH/Chi with the Air Transport Code used for air cargo and passenger transport circuits to Africa and South America.^[193] This code, consisting of two-figure elements from 00 to 99, was successfully decoded by In 7/VI from May 1942 until early 1943, when it was given to the German Air Force, the Luftwaffe.

Work on French traffic 1941-1944

French traffic from 1941 to 1944 was of two main types, Vichy France and Free France. Vichy French traffic which was under the direct control of the French Armistice Commission at Wiesbaden was monitored by the French section of In 7/VI.^[69] By agreement with the vichy government, the French were to inform Germany of their code and cipher procedures, but wary watch was kept on their traffic. The work on Free French traffic which emanated during this period from Free French troops in Syria and in North, West and Equatorial Africa was carried out by OKH/Chi and the Sig. Int. Evaluation centres of KONA 4 in Athens where the traffic was easily intercepted.

In a list compiled by the director of the French section, of the Free French systems worked on by In 7/VI and NAAS 4, the following systems were mentioned as being used in Syria:^[197]

• A 3-Letter system: code table with fortnightly key change. This system appeared from about 1942 to the middle of 1944 in Syria, but was not intercepted after this. Content is described as moderate to good.
• A variant of the above code which passed technical details of wireless traffic. A 3-Letter system: code table with fortnightly key change. Appeared in 1943 to middle of 1944. Sometimes it was used for passing weekly changing call-signs.^[197]
• Police systems which appeared rarely, according to Kühn, that were either 2-Figure substitution tables or simple transpositions.
• A 4-Figure code with daily key change. Appeared in 1944 in the Syrian coastal network. Message traffic described ship movements in the coastal area.

From other sources may be added the de Gaullist's systems, two of which are named: Control Beduoin and Service Politique.^[198] These were initially read from traffic intercept at the French garrison at Bir Hakeim, but had proved impossible until the same cipher was used in Syria by the de Gaulle party.^[198] The work on French systems of KONA 4 was summarised by two members of KONA 4 who stated:

All Syrian traffic was read and a complete picture obtained of the French armed forces^[199]

Among the Free French systems from North Africa which were solved and read by the units were listed by Kühn:^[197]

• 5-Letter messages from a diagonal transposition system with monthly, later semi-monthly changes, used in West Africa from 1943 to 1945. It was later discovered from a captured document that this system has been in use from World War I, and was resurrected evidently for use in West Africa.
• TTSF code. This was a 4-Letter code reciphered by letter substitution into 4 letter cipher text. The first group of the message was always TTSD; the last group the indicator. The code was used in North Africa from 1944 to 1945 for routine messages.
• 5-Letter messages from a diagonal transposition used in Equatorial Africa in 1943–1944.
• 5-Figure messages from a 4-Figure hatted code, designated ATM 43 Sonderführer Hans Wolfgang Kühn, who was Director of Referat 3 of OKH/Chi, notes that ATM 43 derived its name from the fact that it was possible to use the vocabulary of the pre-war French code, the ATM, in the reconstruction of this code.^[197]
• 4-Figure code with subtractor used towards the end of the war, on the Italian front.
• 3-Figure messages from a 4-Figure code with subtractor. This system was used in North Africa in 1944 for transport work.

A 5-Figure de Gaulle code was used in North, West, and Equatorial Africa, and later in France, which had not been solved by the end of the year despite efforts made by In 7/VI from 1941 to 1942.^[200] In 1041 Otto Buggisch stated that he worked on this code for Werner Kunze, a Pers Z S cryptanalyst.^[201] However, no success was obtained, until compromise revealed that the code was transposed with daily changing keys. No further headway was made with this system.

The French section had solved the C-36 and the B-211, the machine cipher similar to the Soviet K-37 cipher machine system, after the French campaign in 1940. When the de Gaullist troops in North Africa and Corsica began to use the C-36 machine for their traffic, the French section already had a solution and it was easily solved during 1943. When a new indicator system based on numbers was introduced in early 1944, a high percentage of the traffic continued to be solved through the use of cribs and statistics. The indicator system itself was broken in the autumn of 1944.^[202]

At the end of the TICOM homework written by Kühn, on the French systems treated by the French section of In 7/VI and KONA 4, Kühn stated that the French section was greatly aided by certain fundamental weaknesses in French cryptography, which lead to easy solutions of most of their systems. These weaknesses were described by Kühn, stated thus:^[203]

• The extraordinary conservatism of the French regarding the construction of their code systems or reciphering methods. Systems which must have been used in World War I, were used in slightly modified form up to 1945, in West Africa. Reciphering methods are regularly of two types: either subtraction with finite subtractors or transposition with keywords taken from the code.
• The habitual use by the French of stereotyped message beginnings and endings which facilitates breaking into the systems.
• The idiosyncrasy of the French of communicating cipher matters or key changes by radio. For instance, through the diagonal system in West Africa, OKH/Chi was able on several occasions to break the key for the C-36 cipher machine and once a key change for the ATM 43 code was announced.

With these weaknesses, it was possible for the French section to read all or most of Free French traffic during the years 1941–1944. Their previous experience with the C-36 and B-211, provided In 7/VI with solutions to the cipher traffic as it was being used by the Charles de Gaulle party. No high grade traffic appears to have been passed by the French during this period.

Work on Swiss, Spanish and Portuguese and Brazilian traffic

From the 1941–1944, the French section of OKH/Chi had subsections for Swiss, Spanish, Portuguese and Brazilian traffic. As Kühn stated, the volume of traffic was small and unimportant.^[61] Otto Buggisch worked with Kunze of Pers Z S on the solution of the Swiss Enigma K.^[204] Although they worked on a theoretical solution of the machine, and applied the solution to trial enciphered text, created by Buggisch himself, the theory was never applied at In 7/VI to Swiss traffic, as the volume of traffic did not warrant the effort.^[205] Moreover, easy solution of the traffic was precluded by the fact that the Swiss did their own wiring of the Enigma wheels and changed these frequently.^[206]

Monitoring of Spanish, Portuguese and Brazilian traffic was coordinated by the French section of the unit,^[49] and was carried out by various KONA field units. From 1939 to 1942, Signal Intelligence Regiment (KONA)#Feste 3, from 1942 to 1943, it was FAK 624 and from 1944, by FAK 624 and Feste 12. The amount of traffic read in these units was evidently small enough to be handled by the personnel stationed there. A Spanish military transposition code and a Spanish digit with variant codes were read. Of seven Brazilians systems known, five were read.^[207]

Work on Italian traffic 1941-1944

From the beginning of the war, the security of the Italian systems was a matter of constant concern to Germany. An Italian section under Captain Dr. Fiala was established in the unit to check the security of Italian traffic, particularly on the route from Italy to North Africa. Germany feared that Afrika Korps troop movements in North Africa, were being betrayed by the insecurity of the Italian codes and ciphers.^[208]

As early as 1941, Dr. Fiala paid a visit to Rome to notify the Italians of the weaknesses of their systems and to request greater security.^[208] The visit made little impression on the Italians who remained confident of their own systems.^[209][210] An attempt to improve Italian security as well as to demonstrate the use of IBM Hollerith machinery section of In 7/VI.^[208] Captain Bigi, who was a cryptanalyst of the Servizio Informazioni Militare, the cipher bureau of the Italian Army was sent, but his report did not result in any changes in Italian cryptography. Captain Bigi's next visit to Berlin met only with coldness on the part of OKH/Chi staff.^[211] By late 1942, the general impression among the Germans was that the Italians were incapable of improving their own systems, even with Inspectorate 7 monitoring them.^[208] The Italian section of the unit was disbanded in 1942 when a leader order (German: führerbefehl) was issued by Hitler.^[212]

In June 1943, with the Armistice of Cassibile (Italy's defection from a German viewpoint) to the Allies, the work on the Italian Referat was restarted at OKH/Chi. The section consisted of small cadre, with Manaigo as section head. Heinz Wolfgang Herzfeld gave an account of this section's work to TICOM. Herzfeld worked on 400 messages that had been intercepted in May, to July 1943. Herzfeld worked on the material which consisted of 5-Figure messages. In the beginning of September 1943, an Italian reciphering table and some messages had been taken from the office of the Italian Commanantura in Athens, arrived in the section. When Benito Mussolini had been arrested, and the armistice had been signed, some German officers of KONA 4, stationed at the Neo Phaliron Velodrome, drove to the Commanantura on Amerikis Street in Athens, walked into the cipher office and started collecting material lying on the tables in the office, and packing it into a case, in front of Italian staff. When Italian officers came in, began shouting, and a scuffle started, the Germans left with the case. The reciphering table was used in the Ellade code and the Piave code.^[212]

In November 1943, the section was again dissolved, this time by Major Lechner.^[212] The decision to disband the section the second time, was justified such that after the fall of Leros, no more Italian wireless traffic was intercepted.

The two codes worked on by the section, in the later period was the Ellade and Piave codes. The enciphering tables captured in Italy enabled the Piave code to be reconstructed and enabled many messages to be captured from Northern Italy. The Ellade code was partly reconstructed when the section was dissolved from lack of current traffic.

At the end of the war, KONA 7 was ordered to cover the traffic of Italian bands in Northern Italy.

Work on Swedish traffic 1941-1944

Work on Swedish Army traffic from 1941 to 1944 was handled by a special detachment of Feste 9 called Out Station Halden, named from the fact that it was located in Halden. For administrative purposes the station was attached to the Halden Police.^[213] According to Bartel, a German cryptanalyst who worked on these systems,^[214] the following Swedish Army systems were worked on:

• SRA 1, SRA 5: A revolving grille system. Numerous cases of compromises occurred and the systems continuously read. First broken in the spring or summer of 1943.
• HGA grille: A more difficult system not read by NAA 11 or Feste 9 in Norway. This was worked on by Pers Z S but without success.
• SC 2: read in May 1943. A simple field code like Slidex.
• SC 3: read in April 1943. Simple, partly alphabetical 3-letter field code without reciphering.
• SC 4: read in June 1943. 3-letter alphabetical code without recipher.

The first Swedish cipher machine (German: Schwedische Maschine 1) (abbr. SM1) was worked on in Norway in 1944 and was identified as similar to a small Hagelin cipher machine like the M-209.^[215] Messages were read at Halden with cribs, by errors in the cryptography, or by having two messages in the same key. The second machine (SM 2) was thought to be a large Hagelin machine. Two copies of the traffic on this machine were made, one for In 7/VI, and one for the station at Halden.^[216] A member of the station at Halden, thought during TICOM interrogation that SM 2 traffic was read.^[216] The intelligence gained from breaking of traffic of SM 1 and the simple field codes allowed Germany, during the spring manoeuvres of Feb-March 1945, to build up a complete tactical picture of the Swedish Army in two months. However, neither the high grade grille (HGA), nor the large Swedish machine was solved.^[213]

Work on Balkan (Southeastern) traffic 1941-1944

Southeastern cryptanalysis was handled at the unit by the Balkan section under the leadership of Rudolf Bailovic and in the field, by KONA. Kona had been stationed in the Balkans area during the entire period of the war, and in addition to its regular task of intercepting the traffic emanating from Syria and North Africa, it had been given the task of monitoring the traffic of the occupied countries in the Balkan area. The Balkan countries whose systems were worked on by the OKH/Chi unit and KONA 4 were: Greece, Hungary, Romania, Yugoslavia, Albania, Turkey and Bulgaria. The work done on the traffic of each of these countries is given below.

Work on Greek traffic 1941-1944

Dr Otto Karl Winkler provided the most information to TICOM regarding Greek ciphers and codes, from a single TICOM home work. Winkler was a translator and cryptanalyst with KONA 4 from the spring of 1941 to May 1945.^[217]

According to Winkler, work on Greek systems started in 1941 when KONA 4 was stationed in Bucharest. The first system was a Greek Air Force system which consisted of a single transposition send in 3-letter groups. Winkler stated that nearly all messages were read by the use of stereo-typed beginnings. Although the messages were of insignificant value, a continuous check on officer personalities, deliveries of stores and information concerning airfields contributed to tactical knowledge of the Greek forces.

KONA 4 worked at this time also on Greek Army and Navy messages, but without success until the conquest of Greece. At that time, Winkler stated Codes were captured which were used by Greeks during the attack on Crete.^[199]

The only other Greek system mentioned as having been attacked in 1941 was a 5-letter code with a cyclic recipherment which Buggisch says he worked on in the unit. Plaintext traffic was becoming rapid when the Greek campaign ended.^[201]

After KONA 4 moved its evaluation centre to Athens in May 1941, no more work was undertaken on these systems until NAAS 4 withdrew from Athens in autumn 1943. At the time, Greek Partisan traffic began to be intercepted. In the spring of 1944, KONA 4 gave Winkler the task of forming a small Greek unit to handle traffic of the traffic of the Greek People's Liberation Army (ELAS). The unit consisted of six people, chief among whom were called Strobl, a cryptanalyst who solved a double transposition system of ELAS while Winkler concentrated on translating the traffic already readable. The work became more important and the unit, now increased to 16 people, was attached to a Close Range Signal Intelligence Platoons NAZ G

Winkler stated that in the beginning the Greeks sent their traffic in two figure substitution with alternative groups.^[218] As few messages were sent on the same substitution, it took several days to break and read these codes. ELAS soon went over exclusively to letter traffic based on double transposition, which was successfully solved largely through the aid given by the carelessness of the Greek cryptographers.

Winkler estimated that 50-60% of the traffic tackled by NAZ G was solved. From these messages, the unit was able to build up an almost complete picture of the organisation and composition of the Greek People's Liberation Army and the National Liberation Front. The unit also compiled lists of leading Greek personalities and officers and informed the competent German political and military authorities about many planned military and political actions, acts of sabotage, ambushes, dynamiting and so on. In addition, the messages provided the exact location of Allied airfields in the Greek mountains, regarding the position, strength and activity of the Allied military missions and various British Commandos, about Greek internal and inter-allied crises and struggles, about the British tactics for the occupation of Greece.^[219]

Work on Greek systems ceased on 15 October 1944 when Naz G was transferred to Sarajevo.^[220]

Work on Hungarian traffic 1941-1944

The Hungarians used the commercial model of the Enigma cipher machine, and had the rotors for the machine made by the German firm of Konski and Krüger. This firm usually turned over the records of the rotor wirings to the Armed Forces Radio Communications Branch (Ag WNV/Fu) which in turn gave them to OKH/Chi. However, Hungarians connected with the firm took the rotors at night and changed the wirings enough to make the firm's records incorrect.^[206] No effort appears to have been made on the part of OKH/Chi to recover the wirings or to prevent the sabotage. It is difficult to suppose that the unit could have been so easily duped had they wished to press the matter. Evidently, they did not consider the traffic worth causing embarrassment to the Hungarians.

With the onset of the war, however, OKH/Chi grew more cautious, particularly with the movement of German soldiers through Hungary.^[221] During the spring and summer of 1941, the radio traffic of the Hungarian State Railways was monitored from a Feste in Tulin. The code being used at that time by the railways was a turning grille (Raster Code) with permanent squares which could be turned in four different positions, and reversed to give four additional positions. The code was solved by Dr S. Döring of the mathematical section of In 7/VI.^[222] After the check of the railway authorities had proved that they were dependable, interception was stopped.^[221]

Watch on Hungarian traffic was dropped from 1941 to 1943 due to the high priority given to Russian traffic.^[208] In 1943, however, interest again developed and a detail was sent from Feste 6, the former Army Fixed Intercept Station at Tulln, to Slovakia, near Bratislava (Pressburg) to monitor Hungarian traffic.^[221] Some tenseness in the relations of Germany and Hungary may be reflected by the fact that all members of the detail wore civilian clothing. Also at that time, OKH/Chi began to resume its work on Hungarian traffic. Count Esterhazy of the Balkan section began work on a Hungarian code and turning grille.^[223] Messages enciphered with a 2-figure substitution key were also worked on.^[224]

Work on Hungarian traffic was done by the Balkan section of OKH/Chi only when the Army thought it necessary to check up on the Hungarian allies, but the attempts that were made were apparently successful. The solution in 1941 by Dr. Döring of the Hungarian grille, while not of great strategic or tactical importance, was characterised by Otto Buggisch as brilliant.^[222]

Work on Rumanian traffic 1941-1944

Very little is known of the work of the Balkan section on Rumanian traffic from 1941 to 1944. According to Mettig, the monitoring of Rumanian traffic ceased in 1941, due to the high priority given to Russian traffic and the chronic shortage of staff.^[208] However, in 1941, monitoring appears to have resumed. In 7/VI stated that Rumanian traffic was completely monitored at that time, and that the Balkan section was reading a Transposition cipher which was decoded with comparative ease.^[225] Other references to Rumanian systems were found in Herzfelds brief statement that the cryptanalysts of the Balkan section were working on Rumanian diplomatic code consisting of 5 or 6 figure groups.^[224] KONA 4 evaluation centre while stationed in Belgrade from September to December 1944 worked on Rumanian traffic.^[198]

Work on Yugoslav traffic 1941-1944

With the insistence of the German government that Yugoslavia align itself with Nazi party policy in the spring of 1941, and the consequent wave of Yugoslav national resistance, the Balkan section of the unit and KONA 4 undertook the heavy burden on monitoring the various types of Yugoslav traffic.

These types were:

• The traffic of the friendly (to Germany) Croatian Home Guard (World War II), (Domobrani) and the Ustaše military units of the puppet government established by Germany in 1941.
• The traffic of the Chetniks under General Draža Mihailović in communication with the Yugoslav government in exile, who resisted German aggression.
• The traffic of the Yugoslav Partisans under Marshall Josip Broz Tito.
• The traffic of the Croatian Peasant Party led by Dr Vladko Maček.

When the German government established the puppet government of Croatia in 1941, the Croats were given the commercial model of the Enigma for use by the Army and Secret police (State Security Administration)^[226] The traffic of these units was read by the Balkan section currently without any delay. According to Buggisch, the solution of this traffic was not an outstanding cryptanalytic achievement for the following reasons:

• The machine used was the Enigma K with three wheels and no stecker or Plugboard.
• The wheels of the machine were wired for the Croats by the German firm of Konski and Krüger which habitually gave the wiring to the Armed Forces Radio Communications who gave them to OKH/Chi.
• A single key was used throughout the entire Croat Army and area, and this consisted of a list of 100 settings per month.
• The ring setting (German: Ringstellung) (Enigma machine#Rotors) of the wheels remained at the position of AAA.
• The wheel order 1,2,3 was always used.

Just to make sure, however, Buggisch added;

the Germans paid for one of the first keys used, and with this decoded traffic were able to establish stereotypes and solve almost 100% of the traffic from the first.^[226]

Although Buggisch did not recall the contents in details, he stated in interrogation that there were some interesting messages about actions against Tito. He also stated that Germany had intended equipping the Croats with the plugboard Enigma, but they had decided against this since they believed the corrupt Croats would continue to sell the keys to British agents.^[202] In that case, OKH/Chi would have to pay for the keys used by the Croats instead of solving them as they could with the commercial Enigma.

Rudolf Hentze of In 7/VI stated that the Balkan section was successful with the double transposition used by Croats but nothing is known of this system.^[227]

Herzfeld stated that the Dombrani and Ustaše used a 5-Figure code based on a former Yugoslav military code.^[223] Evidence is lacking about the actual results obtained but it is probable that the system was solved since the former code was known.

Solution of the systems of General Draža Mihailović and Marshall Josip Broz Tito was divided between a unit of KONA 4 in Belgrade and the Balkan section of OKH/Chi. The breaking of easy guerilla techniques, particularly the solution of daily reciphering, was carried on at Belgrade by a special detachment, NAZ W which had served in 1941 under Wollny as an evaluation centre for Section III Armed Forces Radio Communication Branch (German: Amtsgruppe Wehrmachtnachrichtenverbindungen, Abteilung Funkwesen, Gruppe III) (AgWNV/FU III). With the assumption by the unit of work against the enemies Tito and Mihailović, the detachment came under Army control and was attached to KONA 4.^[228]

The solution of the more difficult systems was carried on at OKH/Chi by the Balkan section under the immediate supervision of Rudolf Bailovic, who was a specialist in Slavic traffic, and a specialist in the systems of Mihailović and Tito.^{[229][230][231]}

Herzfeld, a member of the Balkan section of OKH/Chi from 1941 to the capitulation, had written two reports, or homework for TICOM, specifically I-52 and I-69, that has a full discussion of the Yugoslav systems worked on by that section. The traffic of Mihailović was entirely double transposition with fixed key length and key word.^[232] They were regularly, if slowly, solved at In 7/VI with the aid of stereotyped phrases, frequency charts, and other well known cryptanalytic methods. Herzfeld stated that it took one to three days to break a single message.

The systems of Tito were far more varied, most of them of Russian origin.^[233] In I-69, Herefels lists among the Tito systems broken at In 7/VI as:

• A simple letter or 2-figure substitution system used for enciphering messages sent by brigades and partisan units to Tito divisions in 1944.
• A simple substitution key with short reciphering set used below division level in 1944.
• Simple 2-figure substitution key with nulls and short reciphering set used below division level in northern and western Yugoslavia and Bosnia in 1944, possibly also used in Serbia and Macedonia.
• Multi-columnar substitution key used for traffic between divisions and brigades in Slovenia, western Croatia and western Bosnia in 1944.
• An Albanian multiple substitution key used by Tito partisans of Albanian nationality (National Liberation Movement).
• Variable substitution key with short reciphering set, the main cipher above division until June 1944.

The system which succeeded the variable substitution key with short reciphering set was called Tito's Novo Sifra. It was used after June 1944 above division level and was not broken by In 7/VI. Herzfeld claims that it could have been broken with sufficient traffic and close scrutiny. For a while the new system proved secure but regional commands obviously found it cumbersome and reverted to old insecure systems. Thus the Germans could read a lot of Partisan traffic even after mid-1944. Marshall Tito had close relations with the Soviet Union and during the war he was in constant contact with Moscow through a radio link. This traffic obviously became a target for the Germans and they investigated it in 1944 without finding a theoretical solution.

In the autumn of 1944, work on Tito traffic was increased. Besides the unit stationed in Belgrade under Wollny, the Evaluation Centre of KONA 4 was moved from Athens to Belgrade and began work on Tito ciphers.^[220] NAZ G, which had been working on Greek Partisan traffic was also moved from Thessaloniki to Sarajevo to cover Yugoslav traffic.^[220]

The only reference to the work of the Balkan section of OKH/Chi on Croatian resistance movement ciphers was that they were cryptanalysed by KONA 4 and rechecked by the OKH/Chi Balkan section.^[225]

In general, it may be said that the work on Yugoslav ciphers and codes was successful. The ciphers of Tito and Mihailović formed the most important part of the work of that section with Rudolf Bailovic performing the bulk of the work.

Work on Turkish traffic 1941-1944

Both the intercept and decoding of Turkish traffic was handled largely by signal units subordinate to KONA 4. NAZ T, which was stationed in Graz, worked only in Turkish traffic.^[234] At first it had intercepted Turkish Navy and Merchant Marine traffic as well as Turkish Land Forces and Police traffic, but certain disagreements arose with the Kriegsmarine over the interception of the Navy and the Marine traffic and this was abandoned.^[235]

The police traffic of Turkey is described as:^[236]

• Simple transposition used by the police departments of Ankara, Edirne, Istanbul, İzmir for police matters only
• Two letter or figure code used for police counter-intelligence with police agents
• Two or three letter code used for agent traffic

The Turkish Army codes were mainly transposition codes with a key word, sent in five letter groups preceded by a 4-figure number.^[221] All these systems were decoded by NAZ T and were set to OKH/Chi simply for the purpose of checking all work.^[235]

One special Turkish code is mentioned as having been read by either OKH/Chi or NAZ T, and that was the special code used by the President of Turkey İsmet İnönü, while sailing on the State Yacht, the Savarona. This code was used in 1943 for radio messages, while the President was on the yacht, and not used afterwards.^[221]

Sometime in 1942 to 1943, OKH/Chi received from the Research Office of the Reich Air Ministry (German: Forschungsamt), the mission of solving certain Turkish diplomatic traffic. This the Balkan section did under the supervision of Bailovic, with the decoded traffic being sent to the Forschungsamt. The traffic was used by the military attaches for their reports from Russia, Bulgaria and Italy, and that it was read continually by In 7/VI.^[235] TICOM knew from other sources that this traffic proved to be a very valuable source of information concerning Russia. Mettig remembered a number of reports from the winter of 1943–1944 on the Russian military situation and the preparations for an offensive.^[237] Despite many warnings from British sources that the traffic was being read, Turkey failed to change the system, and the reading of Turkish diplomatic traffic remained a constant source of information.^[237]

Work on agents traffic 1941–1944

The Agents section of OKH/Chi was established in 1942. Before that time, the activities of this section which consisted of radio security inside Germany and monitoring of illegal transmissions had been carried out by Section III of the Armed Forces Signal Communication Group (AgWBNV), Radio Communication Group 3 (German: Amtsgruppe wehrmachtnachrichtenverbindungen) (AgWNV/FU III). The unit was subordinated to Generalleutnant Fritz Thiele.^[6] Thiele was succeeded by Wilhelm Gimmler when Thiele was hanged on piano wire on 4 September 1944 at Plötzensee Prison in Berlin. Gimmler was also later hanged on piano wire for the same event.

In 1942, however, it seemed necessary to establish a deciphering section specialising in agents' ciphers. Fu III wanted to set the unit up within its own organisation but the Supreme Command of the Armed Forces and the Army High Command opposed the establishment of another cryptanalytic agency. As a result of their opposition, it was agreed to set up a section for agents' traffic with an existing cryptanalytic organisation. In 7/VI was chosen as OKW could not spare the personnel, in light of the fact that OKH/Chi had previously raided OKW/Chi for personnel to establish In 7. The agents section was thus attached to OKH/Chi although it appears to have maintained the close relation with Fu III, housing itself near FU III and moving with it, in November 1943 to Jüterbog.^[225]

The agents section was commonly called the Vauck section or Vauck Referat or Referat Vauck and named after its chief cryptanlayist Wilhelm Vauck. Mettig gave great credit to the work of Dr Vauck saying that this section achieved good results because of Vauck's leadership and his personnel cryptanalytic successes. The section was not large consisting of about 35 people in the main section, ten at outposts in Paris and Brussels, and other cities, with eight lent to the Polish section of OKW/Chi. Recognised traffic was decoded in the outstations, the rest was sent to Berlin. All traffic, moreover, was sent to Berlin in duplicate.^[238]

The cryptanalytic methods employed by the Vauck section differed from normal methods of solution because of the peculiar nature of the Agents' systems.^[239] When in spring 1942, when Referat Vauck started work on finding a solution to Allied agents' traffic, it was confronted with a completely new and difficult task. Success could not be achieved using the normal methods of cryptanalysis on Army or diplomatic ciphers. The peculiar construction of agents' ciphers and in particular the frequent changes of ciphers, demanded a new method of approach. Agent cryptographers had not only to be highly enthusiastic about their work and very flexible in their approach, but it was also desirable that a percentage, that was considerably higher than normal cryptography, had to be expert linguists.^[239]

The early research work of the Referat, carried out in close cooperation with the evaluation section of Fu III, was devoted to clarifying the use of Call signs, and to ascertaining systems of indicator groups and coding tables in different procedures. Material, in the shape of old messages which had been gathered in the past, was re-examined. Simultaneously a search began for possible source of compromise within the various ciphers under investigation.^[239]

To supplement this research work an arrangement was made with the appropriate agencies to allow representatives of Referat Vauck to take part in important arrests and in the interrogation of agents. Owing to a shortage of personnel in the Referat it was impossible to take full advantage of this concession. The concession was granted as it was recognised that when an agent was arrested and no cryptographer was present, cipher material, which was usually well camouflaged, was not recognised as such and therefore could not be properly utilised. Furthermore, the material was often not evaluated correctly and delays ensued in forwarding it. Sometimes ambitious amateurs wished to earn credit for themselves by exploiting cipher material. Another danger lay in the fact that when cipher experts were not present, agents might tend to give false or imaginary cipher information. In these cases the presence of an expert was of great value. Agents under interrogation who saw that their cipher methods had been compromised usually gave good signals information. Once the value of Dr Vauck's assistance was recognised, his section were frequently called in to assist the Abwehr and Gestapo in their work.^[240]

It became possible, with the advice of Referat Vauck, either to turn around more agents, or to play back the agent's wireless personality using German personnel. Errors occurred in this field when signals personnel were not present. Thus in the beginning of 1944, it was ascertained that two allied agents, who had been turned around by the Abwehr, were operating in a villa southeast of Bordeaux and were being handed clear messages for encipherment and transmission, without any supervision.^[240]

Work on Czech agents traffic

The Vauck section worked on Agents' traffic of the Czechoslovak Resistance movement.^[228] Mettig believed that the solving of the 1942-1943 of two links running to England made possible the arrest of British agents in Czechoslovakia, one of them a captain. The greatest success was achieved by intercepting the wireless communication of the Czechoslovak Resistance movement in London. This was the only case in which Mettig is certain that it was possible for the Vauck section to solve an agent network by purely cryptanalytic means, and this was largely through breaches of security on the part of the Czech chief. After the system had been solved, the book for enciphering was found and the key recovered. In September 1942, the Czechs were about to go over to a new system, but were foolish enough to name in the old system, the book to be used for enciphering in the new system. Contents of messages solved on this link were nearly always concerned with reports on the political situation and activities of the Czech Resistance Movement, and were so important that for a long time, the W/T traffic was allowed to continue unhindered.

Work on Yugoslav agents traffic

Work on Yugoslav Agents' traffic was carried on by a detachment in Belgrade under Lt. Wollny. This detachment had been under Group III of FU III but was attached in 1942 to KONA 4 because all fighting against hostile organisations such as Draža Mihailović and Josip Broz Tito was directed by the Army.^[241] Traffic which was not solved in this detachment was sent to the Balkan section of OKH/Chi for a solution.

Work on Southern France and Spain agents traffic

Agents' traffic in southern France and Spain emanated largely from the United States, Great Britain and Spanish Republican Army who were in radio contact with stations in Spain. To cope with this traffic, a camouflaged branch station was established in Madrid and the intercepted traffic passed to Referat Vauck for processing.^[242]

Work on Soviet Union Agents traffic

Mettig knew of three important Russian Agents' networks: The Red 3 (German: Die Rote Kapelle), the Schulze-Boysen case, named after its leader, Harro Schulze-Boysen and the two links running from Brussels. Mettig stated that these last named links were, as far as he knew, not solved.^[242] However it was known that this was the Red Orchestra (espionage)#The Trepper Group named after Leopold Trepper who eventually became a double agent, working against the Soviet Union. Mettig perhaps was not privy to this knowledge.

In addition to Mettig's account of the Red 3, two memoranda were written by Wilhelm Fenner, the chief cryptanalyst of OKW/Chi.^[243] Fenner reported that on 23 February 1943, his agency was asked by Vauck section to collaborate in work on certain messages of Soviet agents on the Red 2 net. By the end of March, the Vauck section had furnished Fenner's cryptanalysts, Peter Novopashenny, Trappe and Schmidt, with all the traffic in that system since September 1941 so that a start was made on a solution. Fundamental findings were communicated to OKH/Chi which enabled that organisation to solve the system roughly at the time, as did Fenner's group. After the initial solution, it was agreed that OKH/Chi should continue to work on the system, and Mettig stated that from this help the Vauck section discovered that the system was based on a book text.^[228] In the autumn of 1944, Vauck was reported to have told Mettig that the exact sending position of this net had been determined to be in Switzerland. A raid was planned but had to be cancelled as Swiss authorities had forestalled the Germans. The station, according to Metting, was evacuated and destroyed before the Germans could take action.^[244]

The story of the second Soviet net, the Shulze-Boysen net operating from Berlin in 1942, is equally dramatic.^[244] This net received its name from First lieutenant Russian: Pyatidesyatnik) Harro Schulze-Boysen, whose house was the centre of a communist inspired espionage agency operating on a large scale. When the first inroad into this traffic was made by the Vauck section, Dr. Lenz, one of the members of Vauck's section, mentioned the name Schulze-Boysen to another member of the Vauck section named Haymann who frequented the Schulze-Boysen house. Haymann warned Mrs Schulze-Boysen. Subsequently, both Haymann and Dr. Lenz were arrested, and Haymann condemned to death. Lenz was released and transferred to an out-station in Paris. With the aid of knowledge obtained from decoded traffic, the Gestapo made arrests of from 79 to 80 people of whom 70 were condemned to death. The case was kept strictly secret because many of the accused were employed in various agencies and were betraying secrets to Russia.

Work on Polish resistance movement traffic

The most notable results in the Agents' section were achieved in the interception and solution of the systems used by the Polish Resistance Movement, particularly during the Polish uprising in Warsaw in 1944.^[245] From information passed on this system, the dispositions of the Polish liberation troops as well as friction between them and the Russians could be established. It was possible, moreover, to solve all wireless traffic which the Polish government in London carried on with its organisations in Poland. In order to preserve secrecy and to insure quicker delivery of the solved message traffic, eight members of the Vauck section were transferred in the autumn of 1943 to the Polish section of OKW/Chi for work there. The Plain text was published by the OKW/Chi as Reliable Reports, with an extremely restricted distribution. To ensure complete radio intercept coverage, OKW/Chi ordered its outstation at Lauf an der Pegnitz also to intercept the traffic. Schubert, a cryptanalyst at GdNA, wrote a brief account of the systems used by the Polish resistance movement in which he stated that systems 006, 117, 118 and 181 were broken and that others were worked on. Most of them were simple 2-figure substitutions used without an indicator, with some variations in development and the use of basic keys and key phrases.^[246]

Work on German traitors traffic

Mettig stated that he once saw a report concerning a German who transmitted, by wireless to England, details of a newly constructed signals shelter in Berlin urgently requesting that it be bombed. No details of these were known by TICOM.^[244]

Linguistic research 1941-1944

Linguistic research during the years 1941-1944 was carried on at the OKH/Chi, by the section designated as the Linguistic Research Department (German: Sprachforschungsrefrat). Oberst Metting listed this section as one of the twelve sections of the original unit in 1942.^[36] Köhler was named by Mettig to manage this section in 1942 and Köhler remained head of the unit throughout the war, until November 1944, when the section was transferred from the GdNA to the OKW/Chi.^[247] Mettig claimed that it was contemplated that the members of the linguistic research section would advise the cryptanalysts on language problems and direct all matters of the Armed Forces concerning foreign languages. Although the plans were never realised, the nature of the work of the section can be inferred from these plans. It was known that the section would have had an exceedingly well stocked cryptographic library, including foreign maps in a large number of scales, journals, transport time tables, foreign reference works, extensive biographies of the enemy and other important categories of information related to cryptography in a wide variety of sources.

Mathematical research 1941-1944

According to Metting, Dr. Hans Pietsch was the Director of the Mathematical Research section. Pietsch had managed to collect the best available cryptanalysts, i.e. the best mathematical brains.^[36] The work of this section was twofold:

• The investigation of all unsolved traffic from the various sections of OKH/Chi so long as it was necessary to achieve an inroad by purely analytics means.
• The investigation of the security of current German Army systems.

To achieve these purposes, three subsections were found necessary. Subsections F, 7 and 13 are described above in 5.6.1.

Use of IBM in cryptanalysis 1941-1944

Tabulating machine D11 from the Dehomag company, a German subsidiary of IBM, a type of tabulator, likely used by the In 7/Vi and the GdNA

The Hollerith (IBM) section of OKH/Chi was derived from the IBM section established in 1939-1940 by the In 7/VI, at the suggestion of the mathematicians and former actuaries of this section, who knew Hollerith methods from civil life.^[250] It was natural that in 1942, when the study of the security of the German Army system was transferred from In 7/IV to In 7/VI, the use of Hollerith (IBM) machinery for security studies was transferred to OKH/Chi and quickly adapted for cryptanalytic work on foreign systems. The machinery used by OKH/Chi was mostly of German make, although a number of captured French IBM machines were included in the unit.^[36] The Hollerith section grew considerably in the course of time, both in respect of the number of machines the unit had and of the personnel engaged. In 1943, there were perhaps 20-30 female punchers engaged and about 20-30 soldiers who were Hollerith mechanics and such like in civilian life. Baurat Schencke was in charge.^[250] Hentze stated that in 1944, there were 30 key punchers, and 2 tabulators.^[57]

Some of the bigger Hollerith machines were always being provided with special new wirings for special cryptanalytic purposes, e.g. for non-carrying addition and subtraction in codes work. Most of the tasks, however, consisted of the usual statistic (bigrams, trigrams, chain statistics (German: Kettenstatistic), column statistics (German: Spaltenstatistic) and of simple figure-calculations, e.g. in work on Hagelin machines. Buggisch stated that as a rule, no tasks were undertaken which could not have been carried out by hand by perhaps 100 people in a reasonable time.^[250]

German Army cryptanalysis effort 1945

With the establishment of the GDNA in late 1944, all operational cryptanalysis was carried on by sections 2,3,4 of Group IV of the GdNA. There is no record of any new or difficult systems being solved after late 1944. The main effort of the GdNA was apparently directed to the deciphering of systems already solved and to the simple necessity of finding a place to operate. From February 1945 until the capitulation, Group V of the GdNA was constantly on the move seeking refuge in the south from the Allied advance.