The Indo-Pakistani War of 1971 was the direct military confrontation between India and Pakistan during the Bangladesh Liberation War in 1971. Indian, Bangladeshi and international sources consider the beginning of the war to have been Operation Chengiz Khan, when Pakistan launched pre-emptive air strikes on 11 Indian airbases on 3 December 1971, leading to India's entry into the war of independence in East Pakistan on the side of Bangladeshi nationalist forces, and the commencement of hostilities with West Pakistan. Lasting just 13 days, it is considered to be one of the shortest wars in history.