British India was partitioned at the end of colonial rule. On 15 August 1947 India became independent, and on 14 August the new state of Pakistan had come into being. The provinces of Punjab and Bengal were divided between the two, and the princely states were left to accede to one or the other — a process that was settled quickly in most cases and became a war over Kashmir within two months.
The decision had been made in stages over the preceding three years. The Cabinet Mission of 1946 proposed a federal union with grouped provinces, which the Congress accepted and the Muslim League rejected; the League’s Direct Action Day in August 1946 was followed by large-scale communal violence in Calcutta, Noakhali and Bihar. In February 1947 the British government announced it would transfer power by June 1948, and in March Lord Mountbatten, the new viceroy, advanced the date to August 1947. The plan for partition was published on 3 June and accepted by both the Congress and the League.
The boundary between the two new states was drawn by a commission chaired by Sir Cyril Radcliffe, who arrived in India in July 1947 and had not previously visited the country. The award was published on 17 August, two days after independence, so that the line became known to the people living along it only after the transfer of power.
The transfer coincided with one of the largest and most violent population movements of the twentieth century. Millions moved across the new borders in both directions, and communal violence killed a number that has never been firmly established. The human cost of Partition shaped the politics, demography and memory of the region for generations, and its effects on the border districts were permanent.
Independent India adopted a republican constitution on 26 January 1950. The events of 1947 remain the reference point against which much of modern South Asian history, and the relationship between the successor states, is understood — including the unresolved question of Kashmir, which both countries claim and over which they have fought more than once.
