East Pakistan (Bengali: পূর্ব পাকিস্তান Purbo Pakistan, Urdu: مشرقی پاکستان Mashriqi Pakistan) was a former province of Pakistan that existed between 1955 and 1971. It had an area of 55,126 mi² or (142,776 km²). It replaced the former province of East Bengal, and is now a country called Bangladesh.
Bengal was divided into East and West parts in 1947 when British India was separated into the countries of Pakistan and India, the eastern parts becoming East Bengal, one of the five provinces of Pakistan (the others being West Punjab, Sind, Baluchistan, and Khyber Pakhtunkhwa).
After independence from British rule, East Bengal was ruled by the Pakistani government, which was ruled over by the Pakistani military, which mostly belonged to West Pakistan. Growing anger led to the "One Unit Policy", started in 1955, that put an end to the provinces. Under this policy, West Punjab, Balochistan, Sindh, and the Northwest Frontier were joined under the name of West Pakistan and East Bengal became East Pakistan. For administrative purposes it had four divisions, thirteen districts and fifty-seven thanas in 1970; until it was absorbed into the new country of Bangladesh in 1971.