<P> Three Indian corps were involved in the liberation of East Pakistan . They were supported by nearly three brigades of Mukti Bahini fighting alongside them, and many more fighting irregularly . This was far superior to the Pakistani army of three divisions . The Indians quickly overran the country, selectively engaging or bypassing heavily defended strongholds . Pakistani forces were unable to effectively counter the Indian attack, as they had been deployed in small units around the border to counter guerrilla attacks by the Mukti Bahini . Unable to defend Dacca, the Pakistanis surrendered on 16 December 1971 . </P> <P> The Indian Air Force carried out several sorties against Pakistan, and within a week, IAF aircraft dominated the skies of East Pakistan . It achieved near - total air supremacy by the end of the first week as the entire Pakistani air contingent in the east, PAF No. 14 Squadron, was grounded because of Indian and Bangladesh airstrikes at Tejgaon, Kurmitolla, Lal Munir Hat and Shamsher Nagar . Sea Hawks from the carrier INS Vikrant also struck Chittagong, Barisal and Cox's Bazar, destroying the eastern wing of the Pakistan Navy and effectively blockading the East Pakistan ports, thereby cutting off any escape routes for the stranded Pakistani soldiers . The nascent Bangladesh Navy (comprising officers and sailors who defected from the Pakistani Navy) aided the Indians in the marine warfare, carrying out attacks, most notably Operation Jackpot . </P> <P> On 16 December 1971, Lt. Gen Amir Abdullah Khan Niazi, CO of Pakistan Army forces located in East Pakistan signed the Instrument of Surrender . At the time of surrender only a few countries had provided diplomatic recognition to the new nation . Over 93,000 Pakistani troops surrendered to the Indian forces & Bangladesh Liberation forces, making it the largest surrender since World War II, although the Pakistani Army had fought gallantly according to Indian Army Chief Sam Manekshaw . Bangladesh sought admission in the UN with most voting in its favour, but China vetoed this as Pakistan was its key ally . The United States, also a key ally of Pakistan, was one of the last nations to accord Bangladesh recognition . To ensure a smooth transition, in 1972 the Simla Agreement was signed between India and Pakistan . The treaty ensured that Pakistan recognised the independence of Bangladesh in exchange for the return of the Pakistani PoWs . India treated all the PoWs in strict accordance with the Geneva Convention, rule 1925 . It released more than 93,000 Pakistani PoWs in five months . Further, as a gesture of goodwill, nearly 200 soldiers who were sought for war crimes by Bengalis were also pardoned by India . The accord also gave back 13,000 km (5,019 sq mi) of land that Indian troops had seized in West Pakistan during the war, though India retained a few strategic areas; most notably Kargil (which would in turn again be the focal point for a war between the two nations in 1999). This was done as a measure of promoting "lasting peace" and was acknowledged by many observers as a sign of maturity by India . However, some in India felt that the treaty had been too lenient to Bhutto, who had pleaded for leniency, arguing that the fragile democracy in Pakistan would crumble if the accord was perceived as being overly harsh by Pakistanis . </P> <P> Reaction to the defeat and dismemberment of half the nation was a shocking loss to top military and civilians alike . Few had expected that they would lose the formal war in under a fortnight, and there was also unsettlement over what was perceived as a meek surrender of the army in East Pakistan . Yahya Khan's dictatorship collapsed and gave way to Bhutto, who took the opportunity to rise to power . General Niazi, who surrendered along with 93,000 troops, was viewed with suspicion and contempt upon his return to Pakistan . He was shunned and branded a traitor . The war also exposed the shortcomings of Pakistan's declared strategic doctrine that the "defence of East Pakistan lay in West Pakistan". </P>

Who is heading the indian army during the bangladesh liberation war