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

Direct Action Day was the day the All-India Muslim League decided to take a "direct action" using general strikes and economic shut down to demand a separate Muslim homeland after the British exit from India. Also known as the 1946 Calcutta Riots, it soon became a day of communal violence in Calcutta. It led to large-scale violence between Muslims and Hindus in the city of Calcutta 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, including their short-term consequences, controversy remains regarding the exact sequence of events, the various actors' responsibility and the long-term political consequences.

Kolkata, also known as Calcutta, is the capital and largest city of the Indian state of West Bengal. It lies on the eastern bank of the Hooghly River, 80 km (50 mi) west of the border with Bangladesh. It is the primary financial and commercial centre of eastern and northeastern India. Kolkata is the seventh most populous city in India with an estimated city proper population of 4.5 million (0.45 crore) while its metropolitan region Kolkata Metropolitan Area is the third most populous metropolitan region of India with a metro population of over 15 million. Kolkata is regarded by many sources as the cultural capital of India and a historically and culturally significant city in the historic region of Bengal.