After the Language Movement began in 1952 there was growing discontent in East Pakistan with the rule of West Pakistan. On 25 March 1971, this rising political discontent led West Pakistan to crack down on East Pakistanis with brutal force in a campaign known as 'Operation Searchlight'. In response, East Pakistan declared its independence and set up the state of Bangladesh. This led to the outbreak of civil war, in which millions of people - both Bengali and Urdu speakers - lost their lives. In addition an estimated 10 million refugees flooded across the border into Indian Bengal.
The Bangladesh Liberation War took place from March to December 1971. On 16 December 1971 the allied forces of the Indian army and the Mukti Bahini ('freedom fighters') defeated the West Pakistani army and Bangladesh became an independent nation.