quality:corruption, structural:reformatting
Outbreak of war

Talks broke down on 25 March 1971 when Yahya Khan left Dhaka, declared martial law, banned the Awami League and ordered the Pakistan Army to arrest Mujib and other Bengali leaders and activists. The Pakistan Army launched Operation Searchlight. Mujib sent telegrams to Chittagong where M. A. Hannan from the Awami League and Major Ziaur Rahman from the East Bengal Regiment announced the Bangladeshi declaration of independence on Mujib's behalf. The text of Mujib's telegram sent at midnight on 26 March 1971 stated the following:

This may be my last message, from today Bangladesh is independent. I call upon the people of Bangladesh wherever you might be and with whatever you have, to resist the army of occupation to the last. Your fight must go on until the last soldier of the Pakistan occupation army is expelled from the soil of Bangladesh and final victory is achieved.

Shortly after having declared the independence of Bangladesh, Mujib was arrested without charges and flown to prison in West Pakistan after midnight. Mujib was moved to West Pakistan and kept under heavy guard in a jail near Faisalabad. Sheikh Mujib was later moved to Central Jail Mianwali where he remained in solitary confinement for the entirety of the war. Kamal Hossain was also arrested and flown to West Pakistan while many other League leaders escaped to India. Pakistani general Rahimuddin Khan was appointed to preside over Mujib's court-martial trial, the proceedings of which have never been made public. Mujib was sentenced to death but his execution was deferred on three occasions.

The Pakistan Army's operations in East Pakistan were widely labelled as genocide. The Pakistan Army carried out atrocities against Bengali civilians. With help from Jamaat militias like the Razakars, Al-Badr and Al-Shams, the army targeted Bengali intellectuals, professionals, politicians, students, and other ordinary civilians. Many Bengali women suffered rape. Due to the deteriorating situation, large numbers of Hindus fled across the border to the neighbouring Indian states of West Bengal, Assam and Tripura. Bengali army and police regiments soon revolted and League leaders formed the Provisional Government of Bangladesh. A major insurgency led by the Mukti Bahini arose across East Pakistan. Despite international pressure, the Pakistani government refused to release Mujib and negotiate with him. Mujib's family was kept under house arrest during this period. General Osmani was the key military commanding officer in the Mukti Bahini. Following Indian intervention in December, the Pakistan Army surrendered to the allied forces of Bangladesh and India.