Formation of the intelligence wing during British rule

As the Congress movement was taking off, Dufferin became aware of the inadequacy of the system of collection of political intelligence and saw in the Indian National Congress, a threat to the stability of the empire, as there was no other political movement at that time raging in the country. In response to Dufferin's proposal, the Secretary of State for India issued an order on 22 December 1887 for setting up a Central Special Branch and also Special Branches of the Police Department at the headquarters of each provincial Government.

In the beginning, the Central Special Branch did not have any unit solely under their control. They were merely collating and compiling their reports received from the provincial Special Branches. But in the far-flung areas of the Empire, there was need for collecting military intelligence.

In 1901 it was, therefore, decided that the Central Special Branch which was responsible only for the collection of political intelligence should be expanded to include a small staff of selective detective agents, to be employed to monitor political movements as also to deal with those forms of organised crimes which extended beyond the limits of a single province.

Formation of district Intelligence Branch office

It gradually came to light that the ramification of the underground conspiratorial organisation were not confined to Calcutta alone but had spread to the districts, then the idea of forming Intelligence Branches at district headquarters was seriously considered. As early as in 1908, the Special Branch had set up some centres in places where the existence of underground organisations had come to light. Such centres were at Midnapore, Barishal, Deoghar, Kushtia, Khulna, Jessore. Each of the centres was in-charge of an Inspector who was detailed from Calcutta and remained stationed at the Centre till he was relieved by another. On the eve of the First World War, however, it was felt necessary that there should be a senior officer in-charge of the Intelligence Branch in the districts. In some of the affected districts, Additional Superintendents of Police were posted to head the district Intelligence Branches. Where there was no Additional Superintendent of Police, the Superintendent of Police was designated as Superintendent of Police in-charge of the District Intelligence Branch. The bigger districts like Midnapore, Dhaka, Chittagong etc. had one Additional Superintendent of Police in-charge of the District Intelligence Branch. The duty of the Intelligence Branch of the District Police was twofold:

• The collection of information regarding the ramification of the conspiracy organisation.
• Investigation of the specific offences committed in furtherance to the common object of the conspiracy.

The methodology of collection and dissemination of intelligence and the system of reporting from District Branch to higher-ups were gradually evolved and codified over the years. It, however, goes without saying that the Intelligence Branch in Bengal showed exceptional ability in dealing with the terrorist violence during the period before Independence. Its excellent source work and innumerable channels of information eventually resulted in unearthing of all the groups responsible for terrorist violence.