Proclamation of Bangladeshi Independence

The independence of Bangladesh was declared on 26 March 1971 at the onset of the Bangladesh Liberation War by Bangabandhu Sheikh Mujibur Rahman; the following day the declaration was broadcast by Major Ziaur Rahman in a radio broadcast. On 10 April, the Provisional Government of Bangladesh issued a proclamation on the basis of the previous declaration and established an interim constitution for the independence movement.
First declarations.
On 25 March 1971, negotiations between Pakistani President Yahya Khan and Awami League leader Sheikh Mujibur Rahman broke down after Khan refused to accept Rahman's plan for a new federal constitution in Pakistan. Rahman's party won an absolute majority in the National Assembly during Pakistan's first free election in 1970. However, the newly elected parliament was barred from taking power due to objections from the Pakistani military and the West Pakistan establishment. The Awami League's 6 points proposal for a Pakistani federation was strongly opposed by bureaucrats and senior politicians like Zulfikar Ali Bhutto in West Pakistan. The League initiated a civil disobedience campaign in East Pakistan to press for convening the parliament, amid rising Bengali aspirations for self-determination and independence. On 7 March 1971, Rahman addressed a huge pro-independence rally in Dhaka. Yahya Khan and Bhutto were in the city throughout March for negotiations. The political process was abruptly ended by President Khan, who faced pressure from the military for a crackdown.
In the evening of 25 March, Mujib convened a meeting of senior Bengali nationalist leaders, including Tajuddin Ahmad and Colonel M A G Osmani, at his residence in Dhanmondi. They were briefed by Bengali insiders within the military of an impending crackdown. They implored Mujib to declare independence but Mujib declined to do so fearing he would be tried for treason. Tajuddin Ahmed even brought all the recording instruments but had failed to convince Mujib to record independence declaration. Rather Mujib ordered all the high ups to flee to India. However, Mujib decided to remain in Dhaka in hope of coming to a negotiated compromise with West Pakistan in becoming the Prime Minister of the whole Pakistan.
On the night of 25 March, the Pakistan Armed Forces launched Operation Searchlight in the capital of East Pakistan. Tanks rolled out on the streets of Dhaka. The troops were said to have massacred students and intellectuals in Dhaka University, as well as many civilians in other parts of the city. It set major cities" ablaze and crushed resistance from the police and the East Pakistan Rifles.
Just before his arrest on the night of 25 March, Sheikh Mujibur Rahman sent a message about attacks on EPR and police barracks in Dhaka, and declared the independence of Bangladesh. This message was broadcast from Swadhin Bangla Betar Kendro on 26 March 1971, and was widely reported in newspapers around the world. But according to A K Khandker, the Deputy Chief of Staff of the Bangladesh Armed Forces during the Liberation War, Sheikh Mujib did not record any voice message for the declaration, and according to Tajuddin Ahmed, Sheikh Mujib denied it giving the excuse as for fear of being taken as traitor by Pakistan, and then Pakistan would able to take him under tribunal for that. Sharmin Ahmed Ripi, daughter of Tajuddin Ahmed, also made the same claim in her book "Tajuddin Ahmed: Neta O Pita" (Tajuddin Ahmed: Leader and Father). Khandker also added that, not Zia, but a technician of East Bengal radio station first announced the declaration in radio. Then M. A. Hannan, a politician of Awami League, secondly expressed the announcement. Thirdly, Major Ziaur Rahman, the commander of the East Bengal Regiment in Chittagong, went to the Radio station in Kalurghat, Chittagong on 27 March and declared independence of Bangladesh on behalf of Sheikh Mujibur Rahman.
Constituent Assembly.
On 17 April 1971, the Provisional Government of Bangladesh was formed in Mujibnagar. It converted the elected Bengali members of the national and provincial assemblies of Pakistan into the Constituent Assembly of Bangladesh. The constituent assembly issued a second proclamation of independence, which also served as the fundamental law of Bangladesh until the adoption of the constitution in 1972. This proclamation was drafted by Barrister M Amir-ul Islam and reviewed by Indian Barrister Subrata Roy Chowdhury. The text is given in the following:-