The Partition of India led to the creation on 14 August 1947 and 15 August 1947, respectively, of the sovereign states, Dominion of Pakistan (later Islamic Republic of Pakistan) and Union of India (later Republic of India), upon the granting of independence to British India by the United Kingdom. ‘Partition’ here refers not only to the division of the Bengal province of British India into the Pakistani state of East Bengal (later East Pakistan, now Bangladesh) and the Indian state of West Bengal, as well as the similar partition of the Punjab region of British India into the Punjab province of West Pakistan and the Indian state of Punjab, but also to the division of the British Indian Army, the Indian Civil Service and other administrative services, the railways, and the central treasury, and other assets.
East Bengal celebrates its freedom from British colonial rule as it becomes a province of Pakistan. West Bengal remains with India, which celebrates its own independence the following day.
A mass exodus ensues, especially in Punjab, where Hindus and Muslims feel forced into territories awarded to India and Pakistan, respectively. Communal violence erupts among people uprooted and displaced by a political decision over which they had no control.
Muhammad Ali Jinnah, the leader of the Muslim League, becomes the Governor General of Pakistan, now a member of the British Commonwealth.
* Partition of India and Bengal and Some Myths:
However each was untrue. Read this for details.
Source: Uttorshuri, Wikipedia