During the Bangladesh Liberation War, Bengali nationalists declared independence and formed the Mukti Bahini (the Bangladeshi National Liberation Army). The Provisional Government of Bangladesh was established on 17 April 1971, converting the 469 elected members of the Pakistani national assembly and East Pakistani provincial assembly into the Constituent Assembly of Bangladesh. The provisional government issued a proclamation that became the country's interim constitution and declared "equality, human dignity, and social justice" as its fundamental principles. Due to Mujib's detention, Syed Nazrul Islam took over the role of Acting President, while Tajuddin Ahmad was named Bangladesh's first Prime Minister. The Mukti Bahini and other Bengali guerrilla forces formed the Bangladesh Forces which became the military wing of the provisional government. Led by General M. A. G. Osmani and eleven sector commanders, the forces held the countryside during the war and conducted wide-ranging guerrilla operations against Pakistani forces. As a result, almost the entire country except the capital Dacca was liberated by Bangladesh Forces by late November.This led the Pakistan Army to attack neighbouring India's western front on 2 December 1971. India retaliated in both the western and eastern fronts. With a joint ground advance by Bangladeshi and Indian forces, coupled with air strikes by both India and the small Bangladeshi air contingent, the capital Dacca was liberated from Pakistani occupation in mid-December. During the last phase of the war, both the Soviet Union and the United States dispatched naval forces to the Bay of Bengal in a Cold War standoff. The nine month long war ended with the surrender of Pakistani armed forces to the Bangladesh-India Allied Forces on 16 December 1971. Under international pressure, Pakistan released Rahman from imprisonment on 8 January 1972 and he was flown by the British Royal Air Force to a million-strong homecoming in Dacca. Remaining Indian troops were withdrawn by 12 March 1972, three months after the war ended.