Indo-Pakistani War of 1971

Indian T-55 tanks on their way to Dhaka.

The Indo-Pakistani War of 1971 was a military conflict between India and Pakistan. Indian, Bangladeshi and international sources consider the beginning of the war to be Operation Chengiz Khan, Pakistan's 3 December 1971 preemptive strike on 11 Indian airbases. Lasting just 13 days it is considered one of the shortest wars in history.
During the course of the war, Indian and Pakistani forces clashed on the eastern and western fronts. The war effectively came to an end after the Eastern
 Command of the Pakistani Armed Forces signed the Instrument of Surrender, on 16 December 1971 following which East Pakistan seceded as the independent state of Bangladesh. Between 90,000 and 93,000 members of the Pakistan Armed Forces including paramilitary personnel were taken as Prisoners of War by the Indian Army It is estimated that between 2,000,000 and 3,000,000 civilians were killed in Bangladesh. As a result of the conflict, a further eight to ten million people fled the country at the time to seek refuge in neighbouring India.

The Indo-Pakistani conflict was sparked by the Bangladesh Liberation war, a conflict between the traditionally dominant West Pakistanis and the majority East Pakistanis. The Bangladesh Liberation war ignited after the 1970 Pakistani election, in which the East Pakistani Awami League won 167 of 169 seats in East Pakistan and secured a simple majority in the 313-seat lower house of the Majlis-e-Shoora (Parliament of Pakistan). Awami League leader Sheikh Mujibur Rahman presented the Six Points to the President of Pakistan and claimed the right to form the government. After the leader of the Pakistan Peoples Party, Zulfikar Ali Bhutto, refused to yield the premiership of Pakistan to Mujibur, President Yahya Khan called the military, dominated by West Pakistanis, to suppress dissent.
Mass arrests of dissidents began, and attempts were made to disarm East Pakistani soldiers and police. After several days of strikes and non-cooperation movements, the Pakistani military cracked down on Dhaka on the night of 25 March 1971. The Awami League was banished, and many members fled into exile in India. Mujib was arrested on the night of 25–26 March 1971 at about 1:30 am (as per Radio Pakistan’s news on 29 March 1971) and taken to West Pakistan. The next action carried out was Operation Searchlight, an attempt to kill the intellectual elite of the east.
On 26 March 1971, Ziaur Rahman, a major in the Pakistani army, declared the independence of Bangladesh. In April, exiled Awami League leaders formed a government-in-exile in Baidyanathtala of Meherpur. The East Pakistan Rifles, a paramilitary force, defected to the rebellion. Bangladesh Force namely Mukti Bahini consisting of Niyomito Bahini (Regular Force) and Gono Bahini (Guerilla Force) was formed under the Commander-in-Chief (C-in-C) General Mohammad Ataul Ghani Osmany.