The Indo-Pakistani War of 1971 was a military confrontation between India and Pakistan that occurred during the Bangladesh Liberation War in East Pakistan from 3 December 1971 to the fall of Dacca (Dhaka) on 16 December 1971. The war began with Operation Chengiz Khan's preemptive aerial strikes on 11 Indian air stations, which led to the commencement of hostilities with Pakistan and Indian entry into the war for independence in East Pakistan on the side of Bengali nationalist forces, expanding the existing conflict with Indian and Pakistani forces engaging on both eastern and western fronts. 13 days after the war started, India achieved a clear upper hand, the Eastern Command of the Pakistan military signed the instrument of surrender on 16 December 1971 in Dhaka, marking the formation of East Pakistan as the new nation of Bangladesh. Officially, East Pakistan had earlier called for its secession from Pakistan on 26 March 1971. Approximately 93,000 Pakistani servicemen were taken prisoner by the Indian Army, which included 79,676 to 81,000 uniformed personnel of the Pakistan Armed Forces, including some Bengali soldiers who had remained loyal to Pakistan. The remaining 10,324 to 12,500 prisoners were civilians, either family members of the military personnel or collaborators (Razakars).It is estimated that members of the Pakistani military and supporting pro Pakistani Islamist militias killed between 300,000 and 3,000,000 civilians in Bangladesh. As a result of the conflict, a further eight to ten million people fled the country to seek refuge in India.During the 1971 Bangladesh war for independence, members of the Pakistani military and supporting pro Pakistani Islamist militias called the Razakars raped between 200,000 and 400,000 Bangladeshi women and girls in a systematic campaign of genocidal rape.