The partition of India was the partition of British India on the basis of religious demographics. This led to the creation of the sovereign states of the Dominion of Pakistan (that later split into the Islamic Republic of Pakistan and the People's Republic of Bangladesh) and the Union of India (later Republic of India). The Indian Independence Act 1947 had decided 15 August 1947 as the appointed date for the partition. However, Pakistan came into existence a day earlier, on 14 August.
The Partition of British India was based on the prevailing religions, broadly as shown in this map of 1909.
The partition of India was set forth in the Indian Independence Act 1947 and resulted in the dissolution of the British Indian Empire and the end of the British Raj. It resulted in a struggle between the newly constituted states of India and Pakistan and displaced up to 12.5 million people with estimates of loss of life varying from several hundred thousand to a million (most estimates of the numbers of people who crossed the boundaries between India and Pakistan in 1947 range between 10 and 12 million). The violent nature of the partition created an atmosphere of mutual hostility and suspicion between India and Pakistan that plagues their relationship to this day.
The partition included the geographical division of the Bengal province into East Bengal, which became part of the Dominion of Pakistan (from 1956, East Pakistan). West Bengal became part of India, and a similar partition of the Punjab province became West Punjab (later the Pakistani Punjab and Islamabad Capital Territory) and East Punjab (later the Indian Punjab, as well as Haryana and Himachal Pradesh). The partition agreement also included the division of Indian government assets, including the Indian Civil Service, the Indian Army, the Royal Indian Navy, the Indian railways and the central treasury, and other administrative services.
The two self-governing countries of India and Pakistan legally came into existence at the stroke of midnight on 14â€“15 August 1947. The ceremonies for the transfer of power were held a day earlier in Karachi, at the time the capital of the new state of Pakistan, so that the last British Viceroy, Lord Mountbatten of Burma, could attend both the ceremony in Karachi and the ceremony in Delhi. Thus, Pakistan's Independence Day is celebrated on 14 August and India's on 15 August.