Bangladesh

The Partition of Bangladesh in 1947, was a partition that divided Bengal into the two separate entities of West Bengal belonging to India, and East Bengal belonging to Pakistan. In 1955, East Bengal was renamed East Pakistan, and later became the independent nation of Bangladesh after the Bangladesh Liberation War of 1971.

British India was partitioned in 1947, into the independent states of Pakistan and India. The Province of Bengal was split between them. The western part of the province became the West Bengal state of India and the eastern part became the East Bengal province of Pakistan, with an overwhelming Muslim majority and a large Hindu minority and much smaller minorities of Buddhists and Animists. East Bengal formed one of the five provinces of unified Pakistan.

After independence from British rule, East Bengal was neglected by the central government based in the Western wing, which was at times under military or martial law. A major cause of resentment among the Bengalis was economic exploitation. 

Tensions peaked in 1971, following the cancellation by Pakistani President Yahya Khan of election results that gave the Awami League a majority in the parliament. The Awami League won almost all the seats in East Pakistan, but none in West Pakistan. East Pakistan had more than half the parliamentary seats because it was home to more than half the population. Although the Awami League was in a position to form a government without any coalition partner, it was forced to start negotiations with the Pakistan Peoples Party which had won most of the seats in West Pakistan. The negotiations failed and a 'military government' cancelled the results of the elections in East Pakistan. Under the leadership of Sheikh Mujibur Rahman, Bangladesh began its struggle for independence. The official onset followed a harsh repression carried out by the Pakistan army on Bengali civilians on 25 March 1971. The Bangladeshi government of Sheikh Mujibur Rahman claimed that an estimated 1-3 million Bengalis died during the war between March and December 1971.
Source: Wikipedia Bangladesh and some other websites.