During the rule of the emperor Aurangzeb (reigned 1658–1707), the English East India Company was permitted to establish its base at Calcutta (Kolkata). The British gained strength in the region as the Mughal empire weakened. In 1757, following a battle in the town of Plassey between forces led by British soldier Robert Clive and the Mughal nawab (viceroy) Sirāj-ud-Dawlah, the East India Company emerged as the dominant political power in Suba Bangalah. Under Gov.-Gen. Charles Cornwallis (served 1786–93), a permanent settlement system was established in the territory—now called the Bengal Presidency—whereby property rights were granted in perpetuity to local zamindars (landlords). This property policy indirectly stimulated the growth of a new landed middle class—especially in Calcutta—called the bhandralok. Initially, the bhandralok was dominated by upper-caste Hindus, but the Muslim presence began to increase toward the end of the 19th century. In time, this middle class emerged as the most active advocate of Indian self-government.

The province of Bengal was almost impossible to administer, even after Assam was made a separate province in 1874. In 1905, largely at the initiative of the viceroy George Nathaniel Curzon, two new provinces were created, ostensibly on a geopolitical basis; these provinces were Western Bengal, including Bihar and Orissa, and Eastern Bengal and Assam. With its capital at Calcutta, Western Bengal had a Hindu majority, while the province of Eastern Bengal and Assam, with its capital at Dhaka, was predominantly Muslim. Aside from increasing administrative efficiency, Curzon’s move was intended to position the Muslims as a counterweight to the Hindus.

The partition elicited vociferous protest in Western Bengal, especially in Calcutta, where the Indian National Congress (also called the Congress Party; formed in 1885) played a prominent role. Indian Muslim leaders, however, mostly supported the partition, and in 1906 they gathered at Dhaka under the patronage of Nawab Salimullah and set up the All-India Muslim League. Their efforts secured separate electorates and separate constituencies for the Muslims under the constitutional reforms of 1909, but they could not save the partition. In 1912 the partition was annulled, Bihar and Orissa were constituted into a new province, and Assam reverted to its separate status.

Following the reunification of Bengal, the Congress Party and the Muslim League worked together for self-government; among the leaders of this effort were Nawab Salimullah, Chitta Ranjan Das, Fazl ul-Haq, and Sarat Chandra Bose. Communal animosities resurfaced in the early 1920s, however, in the wake of a failed nonviolent alignment between the Indian Muslim front known as the Khilafat Movement and the Hindu-led Indian nationalist Noncooperation Movement under Mohandas Karamchand (Mahatma) Gandhi. Consequently, in order to achieve political goals, it became necessary to adopt coalition tactics that would transcend communal antagonisms; the politician who proved most adept at this was Fazl ul-Haq, chief minister of Bengal from 1937 to 1943. He set up his own Peasants and Tenants (Krishak Proja) Party and formed a coalition with the Muslim League. In 1940, at the league’s annual gathering at Lahore, Fazl ul-Haq proposed the so-called “Pakistan Resolution,” demanding independent states for Muslims. The following year, however, he was expelled from the Muslim League; he formed a new coalition and continued to serve as chief minister.

In 1942 new rounds of political dialogue commenced, but no agreement could be reached. With legislative elections in 1946, the Muslim League returned to power under the leadership of Hussain Shaheed Suhrawardy, who subsequently became chief minister of Bengal. In August of that year an intense Muslim-Hindu communal conflict erupted in Calcutta, and it eventually spread well beyond the borders of Bengal. This event, combined with protracted and unfruitful discussions between the various groups, made the partition of India appear inevitable. Suhrawardy, Sarat Chandra Bose, and several other prominent political leaders reopened negotiations for a separate, independent, united Bengal.

In March 1947 Louis Mountbatten became the last viceroy of British India, with a mandate to transfer powers. As plans were being formulated for the partition of India, Mohammed Ali Jinnah, a leading figure of the Muslim League, advocated for the formation of a united Bengal; Mountbatten was not against the idea, but Mahatma Gandhi and the Congress Party opposed it. When British colonial rule ended in August 1947, two new countries—India and Pakistan—were born, and Bengal was split between them. West Bengal went to India, and East Bengal formed the eastern wing of Pakistan, which was bisected by a vast tract of northern India.