<P> Guerrilla operations, which slackened during the training phase, picked up after August . Economic and military targets in Dacca were attacked . The major success story was Operation Jackpot, in which naval commandos mined and blew up berthed ships in Chittagong, Mongla, Narayanganj and Chandpur on 15 August 1971 . </P> <P> Bangladeshi conventional forces attacked border outposts . Kamalpur, Belonia and the Battle of Boyra are a few examples . 90 out of 370 BOPs fell to Bengali forces . Guerrilla attacks intensified, as did Pakistani and Razakar reprisals on civilian populations . Pakistani forces were reinforced by eight battalions from West Pakistan . The Bangladeshi independence fighters even managed to temporarily capture airstrips at Lalmonirhat and Shalutikar . Both of these were used for flying in supplies and arms from India . Pakistan sent another five battalions from West Pakistan as reinforcements . </P> <P> Prime Minister Indira Gandhi had concluded that instead of taking in millions of refugees, it was economical to go to war against Pakistan . As early as 28 April 1971, the Indian Cabinet had asked General Manekshaw (Chairman of the Chiefs of Staff Committee) to "Go into East Pakistan". Hostile relations in the past between India and Pakistan added to India's decision to intervene in Pakistan's civil war . Resultantly, the Indian government decided to support the creation of a separate state for ethnic Bengalis by supporting the Mukti Bahini . For this, RAW, helped to organise, train and arm these insurgents . Consequently, the Mukti Bahini succeeded in harassing Pakistani military in East Pakistan, thus creating conditions conducive for a full - scale Indian military intervention in early December . Thus, wary of the growing involvement of India, the Pakistan Air Force (PAF) launched a pre-emptive strike on Indian Air Force bases on 3 December 1971 . The attack was modelled on the Israeli Air Force's Operation Focus during the Six - Day War, and intended to neutralise the Indian Air Force planes on the ground . The strike was seen by India as an open act of unprovoked aggression . This marked the official start of the Indo - Pakistani War . </P> <P> As a response to the attack, both India and Pakistan formally acknowledged the "existence of a state of war between the two countries", even though neither government had formally issued a declaration of war . </P>

Who headed the indian army during the bangladesh liberation war 1971