Netherlands East Indies campaign

Following the Japanese attack on Pearl Harbor, the air echelons of the 11th conducted antisubmarine patrols along the California coast from Muroc Army Air Field, California from 8 to 12 December 1941 before moving on out into the Pacific Theater. Assigned to detached duty to the United States Navy at Brisbane, Australia on 22 December 1941, the squadron flew combat while operating from Hickam Field, Hawaii between 18 December 1941 and 5 January 1942.

Japanese forces attacked the Netherlands East Indies at about the same time the air echelon of the 11th arrived, beginning a battle that ended in the withdrawal of United States forces in early March. During the unsuccessful defense of the Indies, the main body of the squadron flew from Hollandia, meanwhile a detachment operated under Navy control from the Fiji Islands and then from Australia.

Major Austin A. Straubel (4 September 1904 – 3 February 1942) was commander of the 11th Bombardment Squadron and acting commander of the 7th Bombardment Group when he died from burns received in the crash of a B-18 Bolo near Surabaya, Java.^{[8][9][note 2]}

In early March 1942, the 11th withdrew to Melbourne, Australia, remaining there for about a month. In April 1942 the squadron transferred all of its equipment and personnel to the 19th Bombardment Group.

China Air Task Force

The squadron returned to the United States in mid-1942, leaving B-17s in Australia and being re-equipped under the Third Air Force as a North American B-25 Mitchell medium bombardment squadron. With the cadre units in place at Columbia Army Air Base, South Carolina, other personnel began to arrive from various parts of the U.S., by far the biggest contingent coming in from Keesler Field, Mississippi.

While this build-up was going on an advance cadre of the ground element of the 11th were establishing the organization in the China-Burma-India Theater (CBI). That cadre arrived at Karachi Airport, India (now Pakistan) on 20 May 1942, working their way to their staging base at Allahabad Airfield, India, by 27 May, and moving on to Kunming Airport, China by 14 June. The unit was among the first few bomber units in the CBI. The aircraft were readied for flight operations by Air Technical Service Command at Karachi Air Depot and dispatched to Chakulia Airfield, India (now Bangladesh) in December.

In the middle of April 1942, the air element of the 11th, consisting of trained B-25 combat crews, began to arrive at Morrison Field, Florida, as part of Project 157. Each crew was assigned an aircraft. Some two weeks were spent outfitting the B-25s, testing all the apparatus, and getting the crews accustomed to working together. The night of 2 May 1942, the first crews left for overseas, flying along the South Atlantic Ferry Route initially bound for Natal, Brazil. The B-25s were not only completely fitted and ready for immediate combat, but were loaded with a great variety of extra ground equipment for maintaining aircraft and crews. Every one of the aircraft had at least 500 pounds over the maximum weight overload for safe flight and this route had never been flown over by combat crews before, as Air Corps Ferrying Command pilots had flown Mitchells along the route only with gasoline in the fuel tanks carrying little else.

Once reaching Natal, the ferrying route to Accra in the Gold Coast was taken, then across southern Africa to Khartoum, Sudan. The aircraft were then flown through Aden and followed the old British Imperial Airways route around the southern part of Arabia and Iran to Karachi. At Accra, several B-25s picked up formations of six to eight Curtiss P-40 Warhawks which had landed from an aircraft carrier. Many of these same P-40s and pilots later flew escort on missions in China. Three aircraft never reached India and some arrived several months after the others. By the end of May 1942 most of the other crews of Project 157 arrived in Karachi and were assigned to the 11th Bombardment Squadron.

On 2 June 1942, six B-25s left Allahabad on a secret mission of 15 days' duration. Each aircraft carried one extra crewman to act as relief during the expected two weeks' activity. This was to be the first tactical mission of the 11th Bombardment Squadron as a B-25 squadron. That night saw them at Dinjan, India, in the Assam Valley and the western end of the ferry route across the Hump into Southern China. At 0600 hours the next morning the flights took off for Kunming, China, detouring by way of Lashio, Burma. By 10 June, eight B-25s had reached their base at Kunming. The 11th Bombardment Squadron was the first United States air combat unit in China. Until their arrival, only the American Volunteer Group (AVG) was flying combat missions.

Operating under the provisional China Air Task Force (CATF) at Kumming, the first combat mission in China was on 1 July 1942, against shipping in the Hankow area, with AVG fighters flying escort. No opposition of any kind was found. The next day, three B-25s made a return trip to Hankow, this time concentrating on the warehouse and docking facilities.

On 15 September 1942 the 11th was transferred from the 7th Bombardment Group to the 341st Bombardment Group. The 341st Group usually functioned as if it were two groups, with its headquarters and three of its squadrons, the 22d, 490th and 491st Bombardment Squadrons operating under the Tenth Air Force in India and flying missions against the Japanese in Burma until January 1944; when the 341st was redeployed, the 490th was attached to the Tenth AF while the remainder of the Group joined the 11th in China. Throughout 1942–43, the 11th was attached to and received its operational orders from the CATF, which later became the Fourteenth Air Force.^[10][11]

From several airfields in China the group engaged primarily in attacking enemy concentrations and storage areas and in conducting sea sweeps and attacks against inland shipping. They also bombed and strafed such targets as trains, harbors and railroads in French Indochina (now Vietnam) and the Canton-Hong Kong area of China. The 341st Bomb Group received a Distinguished Unit Citation for special success in applying 'Glip' bombing technique (modified from Skip / Glide) against enemy bridges in the Hanoi region of French Indochina.^[10]

In July 1945, selected pilots, navigators and engineer-gunners were sent to Fenni, India for transition training in the Douglas A-26 Invader. After completing training, they flew their A-26s to China and were involved in a move from Yangkai to Laohwangping Airfield when the Pacific War ended before they could fly any combat missions. Three missions to drop leaflets announcing the war's end were performed before the squadron was ordered to India.^[10]

The 11th's A-26 crews remained to ferry their aircraft to Germany, where they would get caught up flying transports moving American personnel headed home to ports of embarkation. The rest of the squadron's personnel sailed back to the United States. The 11th Bombardment Squadron (M) was inactivated on 2 November 1945, the day after the squadron personnel disembarked at Newark, New Jersey.^[10]