<P> Bangladesh was divided into eleven sectors in July, each with a commander chosen from defected officers of the Pakistani army who joined the Mukti Bahini to conduct guerrilla operations and train fighters . Most of their training camps were situated near the border area and were operated with assistance from India . The 10th Sector was directly placed under the Commander in Chief (C - in - C) General M.A.G. Osmani and included the Naval Commandos and C - in - C's special force . Three brigades (11 Battalions) were raised for conventional warfare; a large guerrilla force (estimated at 100,000) was trained . </P> <P> Three brigades (eight infantry battalions and three artillery batteries) were put into action between July and September . During June and July, Mukti Bahini had regrouped across the border with Indian aid through Operation Jackpot and began sending 2000--5000 guerrillas across the border, the so - called Monsoon Offensive, which for various reasons (lack of proper training, supply shortage, lack of a proper support network inside Bangladesh) failed to achieve its objectives . Bengali regular forces also attacked BOPs in Mymensingh, Comilla and Sylhet, but the results were mixed . Pakistani authorities concluded that they had successfully contained the Monsoon Offensive, which proved a near - accurate observation . </P> <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> <Table> <Tr> <Td> <P> Major battles </P> <Ul> <Li> Battle of Boyra </Li> <Li> Battle of Garibpur </Li> <Li> Battle of Dhalai </Li> <Li> Battle of Hilli </Li> <Li> Battle of Kushtia </Li> </Ul> </Td> </Tr> </Table>

Why was there a civil war in east pakistan