On 16 August 1946, the Muslim League, which demanded the partition of India into two states (Hindu India and Muslim Pakistan), announced a general strike (hartal) which triggered massive riots and numerous casualties in Calcutta in the province of Bengal.
Muslims made up only 23 percent of the population in the city, and relations between Hindus and Muslims were openly hostile. The “Direct Action Day” declared by the Muslim League led to three days of riots and violence: 4,000 Calcutta residents were killed, while 100,000 were left homeless. This marked the beginning of a Muslim-Hindu confrontation in the entire agonising colony. British India was split into two states, India and Pakistan, with the conflict between them continuing in a latent form to this day.
Muhammad Ali Jinnah, leader of the All India Muslim League, also demanded the annexation to the Muslim state of territories where Hindus were then in the majority, Hyderabad and Junagadh in particular. On 14 August 1947, the transfer of power from the British to the Muslims in the newly formed Dominion of Pakistan took place in Karachi, the next day India officially gained independence.
Source:
Gyanendra Pandey, “Remembering Partition: Violence, Nationalism and History in India”, Cambridge: Cambridge University Press, 2002.