The Dominion of Pakistan comprised two geographically and culturally separate areas to the east and the west with India in between.The western zone was popularly (and for a period, also officially) termed West Pakistan and the eastern zone (modern-day Bangladesh) was initially termed East Bengal and later, East Pakistan. Although the population of the two zones was close to equal, political power was concentrated in West Pakistan and it was widely perceived that East Pakistan was being exploited economically, leading to many grievances. Administration of two discontinuous territories was also seen as a challenge.

In 1958 General Ayub Khan suspended the constitution and imposed martial law. By 28 July 1969, President Yahya had set a framework for elections that were to be held in December 1970. Finally, the general elections were held in all over the country on 7 December 1970. In these elections  Bangladesh Awami League, the largest East Pakistani political party, led by Sheikh Mujibur Rahman, won a landslide victory in the national elections. The party won 167 of the 169 seats allotted to East Pakistan, and thus a majority of the 313 seats in the National Assembly. This gave the Awami League the constitutional right to form a government. However, Zulfikar Ali Bhutto (a former Foreign Minister), the leader of the Pakistan Peoples Party, refused to allow Rahman to become the Prime Minister of Pakistan. Yahya Khan declared martial law, banned the Awami League and ordered the army to arrest Mujib and other Bengali leaders and activists.

General Tikka Khan was flown into Dacca to become Governor of East Bengal. East-Pakistani judges, including Justice Siddique, refused to swear him in. A planned military pacification carried out by the Pakistan Army – codenamed Operation Searchlight – started on 25 March to curb the Bengali independence movement by taking control of the major cities on 26 March, and then eliminating all opposition, political or military, within one month. Before the beginning of the operation, all foreign journalists were systematically deported from East Pakistan.

Sheikh Mujib was arrested on the night of 25–26 March 1971 at about 1:30 am (as per Radio Pakistan’s news on 29 March 1971)  and taken to Pakistan after midnight via Tejgaon international airport on a PAF C-130 flight right under the noses of ATC Officer Squadron Leader Khaja, Senior Operations Officer Wing Commander Khademul Bashar and Director of Airport and Flight Security Squadron Leader M. Hamidullah Khan. All were on duty that night due to the state of emergency. Mujib was moved to West Pakistan and kept under heavy guard in a jail near Faisalabad (then Lyallpur). Yahya Khan appointed Brigadier (later General) Rahimuddin Khan to preside over a special tribunal prosecuting Rahman with multiple charges. The tribunal’s sentence was never made public, but Yahya caused the verdict to be held in abeyance in any case. Other Awami League leaders were arrested as well, while a few fled Dacca to avoid arrest.  .Independence of Bangladesh was declared by  Sheikh Mujibiur Rahman few minutes before he was arrested by Pakistani occupation army. At 2.30 pm Independence of Bangladesh was declared by Awami league leader of Chittagong M. A. Hannan on behalf of Bongobondhu Sheikh Mujibur Rahman from Kalurghat. This is Bangladesh’s official Independence Day.

A formal military leadership of the resistance was created in April 1971 under the Provisional Government of Bangladesh. The military council was headed by General M. A. G. Osmani and eleven sector commanders. The Bangladesh Armed Forces were established on 4 April 1971. In addition to regular units, such as the East Bengal Regiment and the East Pakistan Rifles, the Mukti Bahini also consisted of the civilian Gonobahini (People’s Force).The most prominent divisions of the Mukti Bahini were the Z Force led by Major Ziaur Rahman, the K Force led by Major Khaled Mosharraf and the S Force led by Major K M Shafiullah. Awami League student leaders formed militia units, including the Mujib Bahini, the Kader Bahini and Hemayet Bahini. The Communist Party of Bangladesh, led by Comrade Moni Singh, and activists from the National Awami Party also operated several guerrilla battalions.The Pakistan Army, which had the backing of Islamists, created radical religious militias – the Razakars, Al-Badr and Al-Shams – to assist it during raids on the local populace.The Provisional Government of Bangladesh was formed on 17 April 1971 in Mujibnagar and moved to Calcutta as a government in exile.

This chaos  and opression of Bangladeshis continued till  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.On 23 November 1971, the Indian Army conventionally penetrated to the eastern fronts and cross the East Pakistan’s borders to join their Bengali nationalist allies. The strategy adopted was a swift, three-pronged assault of nine infantry divisions with attached armoured units and close air support that rapidly converged on Dhaka, the capital of East Pakistan .Lieutenant General Jagjit Singh Aurora, the GOC-in-C of the India’s Eastern Command, led the Indian full thrust into East Pakistan and as the Indian Eastern Command attacked the Pakistan Eastern Command, the Indian Air Force rapidly destroyed the small air contingent in East Pakistan and put the Dhaka airfield out of commission. In the meantime, the Indian Navy effectively blockaded East Pakistan.Indian Army encircled Dacca and ultimately issued an ultimatum to surrender in “30-minutes” time window on 16 December 1971. Upon hearing the ultimatum, the Pakistan Eastern Command led by its commander Lieutenant-General A.A.K. Niazi stationed in East Pakistan surrendered without putting a fight or offering any resistance.On 16 December 1971, Pakistan ultimately called for unilateral ceasefire and surrendered its combined military to Indian Army .Over 93,000 Pakistani troops surrendered to the Indian forces & Bangladesh Liberation forces, making it the largest surrender since World War II.After Bangladesh’s liberation, Rahman was released from Pakistani custody and returned to Dhaka in January 1972.

Rahman became the Prime Minister of Bangladesh under a parliamentary system adopted by the new country. His government enacted a constitution proclaiming socialism and secular democracy. The Awami League won a huge mandate in the country’s first general election in 1973.