<P> Rural and urban areas across East Pakistan saw extensive military operations and air strikes to suppress the tide of civil disobedience that formed following the 1970 election stalemate . The Pakistan Army, which had the backing of Islamists, created radical religious militias--the Razakars, Al - Badr and Al - Shams--to assist it during raids on the local populace . Members of the Pakistani military and supporting militias engaged in mass murder, deportation and genocidal rape . The capital Dhaka was the scene of numerous massacres, including the Dhaka University killings . An estimated 10 million Bengali refugees fled to neighboring India, while 30 million were internally displaced . Sectarian violence broke out between Bengalis and Urdu - speaking immigrants . An academic consensus prevails that the atrocities committed by the Pakistani military were a genocide . </P> <P> The Bangladeshi Declaration of Independence was proclaimed from Chittagong by members of the Mukti Bahini--the national liberation army formed by Bengali military, paramilitary and civilians . The East Bengal Regiment and the East Pakistan Rifles played a crucial role in the resistance . Led by General M.A.G. Osmani and eleven sector commanders, the Bangladesh Forces waged a mass guerrilla war against the Pakistani military . They liberated numerous towns and cities in the initial months of the conflict . The Pakistan Army regained momentum in the monsoon . Bengali guerrillas carried out widespread sabotage, including Operation Jackpot against the Pakistan Navy . The nascent Bangladesh Air Force flew sorties against Pakistani military bases . By November, the Bangladesh forces restricted the Pakistani military to its barracks during the night . They secured control of most parts of the countryside . </P> <P> The Provisional Government of Bangladesh was formed on 17 April 1971 in Mujibnagar and moved to Calcutta as a government in exile . Bengali members of the Pakistani civil, military and diplomatic corps defected to the Bangladeshi provisional government . Thousands of Bengali families were interned in West Pakistan, from where many escaped to Afghanistan . Bengali cultural activists operated the clandestine Free Bengal Radio Station . The plight of millions of war - ravaged Bengali civilians caused worldwide outrage and alarm . The Indian state led by Indira Gandhi provided substantial diplomatic, economic and military support to Bangladeshi nationalists . British, Indian and American musicians organised the world's first benefit concert in New York City to support the Bangladeshi people . Senator Ted Kennedy in the United States led a congressional campaign for an end to Pakistani military persecution; while US diplomats in East Pakistan strongly dissented with the Nixon administration's close ties to the Pakistani military dictator Yahya Khan . </P> <P> India joined the war on 3 December 1971, after Pakistan launched preemptive air strikes on North India . The subsequent Indo - Pakistani War witnessed engagements on two war fronts . With air supremacy achieved in the eastern theatre and the rapid advance of the Allied Forces of Bangladesh and India, Pakistan surrendered in Dacca on 16 December 1971 . </P>

Who was the heading the indian army during the bangladesh liberation war 1971