The decolonization or independence of India and Pakistan from the British Empire occurred simultaneously with these nations' division from each other according to the Mountbatten Plan of 1947.
Pakistan was founded as a homeland for Muslims.
India was founded as a secular nation, but its large Hindu majority and Hindu fundamentalist movements frightened
In the weeks before and after official partition and independence date of 15 August 1947, approximately 14.5 million people crossed the borders to what they hoped was relative safety with their religious majority.
Based on 1951 Census of displaced persons, . . .
7,226,000 Muslims moved to Pakistan from India.
7,249,000 Hindus and Sikhs moved to India from Pakistan.
Estimates of the number of deaths associated with violence and deprivation from the Partition range from 200,000 to one million, thus app. 500,000 deaths. (cf. US Civil War app. 800,000 deaths)
Regions most devastated by partition:
Punjab region in Northwest, the "breadbasket of India" where Train to Pakistan takes place. Punjab, home to a large Sikh population, was divided between Pakistan and India, with most Sikhs choosing to live in India.
Bengal region near Southeast coast, great cultural center and port where the East India company first began colonizing, divides to West Bengal state of India and East Bengal, which becomes East Pakistan (1947) and Bangladesh (1971).
Below: Map of partitioned India, with Bengal at right
Below: close up of Bengal partition of 1947