Mass riots in Kolkata begin; more than 4,000 people would be killed in 72 hours.

Direct Action Day (16 August 1946), also known as the 1946 Calcutta Killings, was a day of nationwide communal riots. It led to large-scale violence between Muslims and Hindus in the city of Calcutta (now known as Kolkata) in the Bengal province of British India. The day also marked the start of what is known as The Week of the Long Knives. While there is a certain degree of consensus on the magnitude of the killings (although no precise casualty figures are available), including their short-term consequences, controversy remains regarding the exact sequence of events, various actors’ responsibility, and the long-term political consequences.Controversy still rages about the respective responsibilities of the two main communities, the Hindus and the Muslims, in addition to individual leaders’ roles in the carnage. The dominant British view tends to blame both communities equally and single out the calculations of the leaders and the savagery of the followers, amongst whom there were criminal elements. In the Congress’ version of the events, the blame tends to be squarely laid on the Muslim League and in particular on the Chief Minister of Bengal, Suhrawardy. The view from the Muslim League side, nowadays partly upheld in Bangladesh, the successor state to East Pakistan, is that in fact Congress and the Hindus used the opportunity offered by Direct Action Day to teach the Muslims in Calcutta a lesson and kill them in great numbers. Thus, the riots opened the way to a partition of Bengal between a Hindu-dominated Western Bengal including Calcutta, and a Muslim-dominated Eastern Bengal (nowadays Bangladesh).The All-India Muslim League and the Indian National Congress were the two largest political parties in the Constituent Assembly of India in the 1940s. The Muslim League had demanded, since its 1940 Lahore Resolution, that the Muslim-majority areas of India in the northwest and the east, should be constituted as 'independent states'. The 1946 Cabinet Mission to India for planning of the transfer of power from the British Raj to the Indian leadership proposed a three-tier structure: a centre, groups of provinces, and provinces. The "groups of provinces" were meant to accommodate the Muslim League demand. Both the Muslim League and Congress in principle accepted the Cabinet Mission's plan. However, Muslim League suspected that Congress's acceptance was insincere.Consequently, in July 1946, it withdrew its agreement to the plan and announced a general strike (hartal) on 16 August, terming it Direct Action Day, to assert its demand for a separate homeland for Indian Muslims out of certain northwestern and eastern provinces in colonial India. Calling for Direct Action Day, Muhammad Ali Jinnah, leader of the All India Muslim League, said that he wanted “either a divided India or a destroyed India”.Against a backdrop of communal tension, the protest triggered massive riots in Calcutta. More than 4,000 people lost their lives and 100,000 residents were left homeless in Calcutta within 72 hours. This violence sparked off further religious riots in the surrounding regions of Noakhali, Bihar, United Provinces (modern Uttar Pradesh), Punjab, and the North Western Frontier Province. These events sowed the seeds for the eventual Partition of India.