Unlike Punjab, Bengal's partition did not produce a single exchange of populations but a slow outflow that continued for two decades. Riots in East Bengal and in Calcutta in early 1950 killed thousands and pushed hundreds of thousands across the border in a few months, prompting the Nehru-Liaquat Pact of April 1950, under which both governments undertook to protect minorities and allow returns; the pact slowed but did not stop the movement. Departures continued through the 1950s under pressure from land and property measures culminating in East Pakistan's Enemy Property rules, from local violence and from the insecurity of minority status. Riots following the theft of a relic from the Hazratbal shrine in Kashmir in December 1963 set off further killings in Khulna and Dhaka and a fresh exodus in 1964, with several hundred thousand crossing into India and reciprocal movement of Muslims out of West Bengal and Assam. The refugees reshaped Calcutta, Tripura and the Assam valley and left a politics of citizenship and documentation that remains unresolved.
Communal violence, property law and official pressure in East Pakistan pushed Hindus into India, with reciprocal movement of Muslims from West Bengal and Assam
The 1951 census recorded about 41.9 million people in East Bengal, of whom roughly 22 per cent — about 9.24 million — were Hindus, down from about 28 per cent at the 1941 census. By the 1961 census the Hindu share had fallen to 18.5 per cent and by 1974 to 13.5 per cent, the decline reflecting the continuing exodus rather than differential mortality.
The range covers the 1950 riots in East Bengal and Calcutta, for which contemporary Indian and Pakistani estimates diverged by a factor of several, and the 1964 Khulna and Dhaka riots, where reported tolls ranged from a few hundred in official accounts to several thousand in press and refugee testimony. No independent count was made of either episode.
Contemporary press reporting, Indian and Pakistani official correspondence around the Nehru-Liaquat Pact, and later scholarship document killings, abductions and the burning of homes in both 1950 and 1964.
Bangladesh, India