Liberation war and independence
After the partition of the British Indian Empire in 1947, Bangladesh was integrated in Pakistan which was known as East Bengal until 1955 and thereafter as East-Pakistan following the One Unit program.
Bilateral relations between the two wings grew strained over the lack of official recognition for the Bengali language, democracy, regional autonomy, disparity between the two wings, ethnic discrimination, and the central government's weak and inefficient relief efforts after the 1970 Bhola cyclone, which had affected millions in East Pakistan. These grievances led to several political agitations in East Bengal and ultimately a fight for full independence. In March 1971, the Pakistan Armed Forces began "Operation Searchlight," which targeted intellectuals, political activists, Hindus and other minorities. The number of people killed by Pakistani forces remains disputed, with estimates ranging from 300,000 to 3 million. About 8-10 million people became refugees in India. Many Bengali policemen and soldiers mutinied and nationalists formed a guerrilla force, the Mukti Bahini with Indian and Soviet support. When a declared war broke out between East Pakistan and West Pakistan in December 1971, the joint forces of Indian Army and Mukti Bahini later known as Bangladesh Armed forces defeated Pakistani forces in East Pakistan and the independent state of Bangladesh was created.
1974–2012: Establishment and growth of bilateral relations
The left-oriented Pakistan Peoples Party (PPP) led by Zulfikar Ali Bhutto, who had been the main political opponent of Sheikh Mujibur Rahman, came into power in the aftermath of Bangladesh's separation from Pakistan. Initially, Pakistan was not in favour of recognizing Bangladesh and urged other states to hold back their recognition until Pakistan could enter into a dialogue with Bangladeshi leadership. Bangladesh on its part insisted recognition as a pre-condition for dialogue. In 1972, Pakistan left the Commonwealth after some members of the Commonwealth extended membership to Bangladesh. Pakistan also severed ties with other countries which recognized Bangladesh.
On the issue of Bangladesh's application for membership to the UN, China, on Pakistan's request, exercised its veto power for the first time to stall the move, which helped Pakistan to secure in a bargain the release of its Prisoners of War and the return of troops to their prewar positions.
In 1974, the relationship between Bangladesh and Pakistan thawed. Sheikh Mujibur Rahman withdrew the bans on some pro-Pakistan organisations that had operated before Bangladesh's independence. Mujib visited Lahore for an OIC Islamic summit, and in return the Parliament of Pakistan authorised Bhutto to extend recognition to Bangladesh. In June 1974, Pakistani Prime Minister Zulfiqar Ali Bhutto visited Bangladesh and paid homage to Bangladesh's war memorial at Savar Upazila. Both nations discussed an agreement in 1975 in which Bangladesh agreed to take up half of Pakistan's pre-1971 external reserves provided Bangladesh received half of the country's pre-1971 assets and credit went unresolved.
Relations improved considerably under the governments of Ziaur Rahman and Hossain Mohammad Ershad in Bangladesh, which had grown more distant from its usual allies, like India and Russia. Five Pakistani heads of government have made official visits to Bangladesh since the 1980s and numerous trade and cultural agreements have been signed. Common concerns over terrorism have influenced strategic cooperation leading to a gift of several squadrons of F-6 fighter aircraft to the Bangladesh Air Force in the late 1980s although there was no serious effort to maintain them as they were later left to be destroyed by a cyclone. Trade between the two countries currently stands at $340 million which was described by the Deputy High Commissioner of Bangladesh, Ruhul Alam Siddique as 'negligible when taking into account the combined population' (of both countries). Areas he hoped would induce investment from Pakistan to Bangladesh included the textiles and energy sectors.
In 1985, Pakistani President Muhammad Zia-ul-Haq visited the Bangladeshi war memorial, and said "Your heroes are our heroes." Bangladeshi President Erhsad visited Islamabad in 1986. In 1998, Prime Minister Sheikh Hasina visited Pakistan. In July 2002, Pakistani General Pervez Musharraf also visited the war memorial and said "Your brothers and sisters in Pakistan share the pain of the events of 1971."