Lots of Pakistanis blame Yahya Khan and Bhutto for the 1971 debacle. While its true both had a role, I am concerned with the fact that Mujib and especially his party the Awami League are given a clean chit in our discussions. The Awami League was a Bengali nationalist party. The economic and political grievances they had were shared by right-wing pro-Pakistan parties in Bengal as well. But unlike the Awami League they did not commit treason. Why? Because of the ideology they had. They were willing to give Pakistan a chance and more time.
Bengali ethnic nationalism and opposition to the two-nation theory was the real cause of the 1971 debacle. Pro-Pakistan Bengali professor Dr Syed Sajjad Hussain states the same in his book "Wastes of Time." He has narrated the rise of Bengali nationalism and propaganda against the ideology of Pakistan which was carried out on a massive level in East Pakistan through the educational system and media - even with the unwitting aid of the Pakistani Government and pro-leftist civil servants such as Altaf Gahaur.
One of the best accounts of the political developments which led to the separation of East Pakistan is "The Last Days of United Pakistan" by Golam Wahed Chowdhury who was a Bengali adviser of Yahya Khan. He had first hand knowledge and insight into the political developments at the top in 1969-1971. He identifies Mujib as the premier culprit for the breakup of Pakistan. He says that he realised from discussions with him that Mujib was more interested in creating a separate Bangladesh than becoming leader of United Pakistan. The other leader he blames is Bhutto - saying he wanted power whether it be a united Pakistan or divided Pakistan. But he blames Mujib for treason more because of his collaboration with India. However, when it comes to Yahya Khan Golam Wahed Chowdhury tells us that the man was sincere but just incompetent.
I will summarise Golam Wahed Chowdhury in dot points
*During the 1965 war against India, Mujib and his henchmen in the Awami League showed utter disregard for national security and defence. When the Pakistani Government requested him for support during the war Mujib instead made treasonous remarks. Some members of the Awami League were also partaking in treasonous activities during the 1965 war. (G. W. Chowdhury quotes Mujib telling him on a later occasion that he had "no dispute with India.")
*Less than six months after the war the Awami League proposed the "Six Points" plan which envisioned Pakistan as a loose confederation. It was a veiled scheme for secession and it was opposed even by the right-wing Bengali Muslims who shared the Awami League's economic grievances and demands for autonomy.
*A detailed reading of the Six Point proposal shows that under it the federal government would only have a paper role. It would only be able to maintain control over defence and foreign affairs, but would have no financial resources to fulfil its duties even with regards to those two subjects.
*In 1968 the Pakistani Government arrested a number of persons including Mujib in connection with the Agartala Conspiracy Case but the case had to be dropped by the Government due to a popular uprising in East Pakistan without even completing the case.
*In 1969 Ayub Khan resigned and was replaced by Yahya Khan. The country was under martial law and the constitution had been abrogated. Yahya Khan acknowledged the economic and political grievances of Bengalis and was sincere in his wish to rectify them.
*Even the majority of the ruling military junta were also willing to give maximum autonomy to East Pakistan provided it would remain within united Pakistan.
*While its true that some of the generals had concerns about an unconditional transfer of power to civilian politicians and they were also concerned with Mujib's six-point plan (as were non-Awami League Bengalis), but generally from March 1969 to December 1970, the ruling military junta gave Yahya Khan a free hand in his negotiations with the politicians for the transfer of power within the framework of a united Pakistan.
*Since there was no Constitution at the time, a Legal Framework Order was instituted in 1970 so that there could be a legal basis for the elections. The National Assembly which would be elected as a result of these elections would draft the new Constitution of Pakistan.
*The conditions in the LFO were that Islam would be the ideology of Pakistan, the country would remain united, all the provinces would have autonomy but there would be sufficient powers left with the Federal Government for it to function. All parties including the Awami League signed this document.
*[G.W. Chowdhury notes here that while the Awami League pledged its allegiance to the Islamic ideology of Pakistan when it signed the 1970 LFO agreement, it went on to impose secularism on Bangladesh after its independence.]
*Mujib also promised to show Yahya Khan his party's draft constitution for Pakistan after the elections. Mujib promised Yahya Khan that he would modify and soften his Six Points scheme after the election.
*Yahya Khan also dissolved the parliament's rule of parity which gave West and East Pakistan an equal number of seats in favour of "One man, One vote" system which meant that East Pakistan could dominate the national assembly due to its larger population.
*During the year long election campaign in 1970, Mujib would publicly reaffirm his loyalty to united Pakistan. But he was not sincere.
*Intelligence services in 1970 managed to secretly tape record Mujib's discussion with his Awami League cabinet in which he said that his aim was to create Bangladesh anyway and after the elections he would tear up the LFO agreement when no one would be able to challenge him. He also referred to "foreign" (presumably Indian) help.
*Both G W Chowdhury and Yahya Khan clearly heard Mujib's voice in the recording but Yahya Khan took no action due to his incompetence.
*Right wing "Islam-pasand" (Islam-loving) political parties found it difficult to campaign in East Pakistan. Militant Awami Leaguers would disrupt and attack their meetings and rallies and the entire Bengali elite and press was on the Awami League's side.
*Even though separatist talk was outlawed by a martial law regulation, Awami Leaguers were preaching the secession of "Bangladesh" and Bengali nationalism all over East Pakistan. For example in a meeting on 14 August Dacca University students displayed the Bangladeshi flag and a map of the new country. The meeting was presided over by the university's Vice-Chancellor. When the martial law administrator Lieutenant General Yakub Khan summoned the Vice-Chancellor to explain this, the naive and incompetent Governor Admiral Ahsan intervened to save the Vice-Chancellor.
*Martial Regulation 60 banned all political groups and individuals from speaking against Pakistan's Islamic ideology or inciting regional hatred. But the Awami League breached this regulation the most and openly and violently preached regional hatred during the election campaign. Yahya Khan's repeated pleas for tolerance were ignored.
*Both foreign and Pakistani intelligence services were reporting the flow of money and arms from India to the Awami League during the election campaign to prepare it for confrontation with the Pakistan Army. Non-Awami League Bengali politicians also gave the government similar reports.
*But the incompetent Governor Ahsan was too optimistic and assured Yahya Khan that Mujib would not break up Pakistan. Yahya Khan believed Ahsan's false optimism.
*Mujib assured Yahya that the Six Points did not mean a division of the country. Yahya believed him. But G W Chowdhury obtained a copy of the premilinary draft of the Awami League constitution and saw that there was no hope for a true federal union in its six points.
*After the Bhola cyclone many Bengali politicians appealed to Yahya Khan to postpone the elections. But Mujib opposed any postponement. He also threatened that 1 million people would be killed in a confrontation if the election was postponed. Yahya gave into Mujib's blackmailing. Mujib won most East Pakistani seats.
*G W Chowdhury observed that most West Pakistanis and Army officers did not have a problem with Mujib becoming Prime Minister, as long as he would keep the country united. Many quarters even described him as "future prime minister" of Pakistan. But Mujib refused to visit West Pakistan which gave the impression to some that Mujib did not really want to become Prime Minister of a united country.
*Yahya Khan held talks with Mujib in January 1971 and described Mujib as the future Prime Minister of Pakistan.
*But in his talks with Yahya in January 1971 after the elections, Mujib refused to show Yahya Khan his party's draft
constitution, contrary to his earlier promise that he would do so.
*G W Chowdhury reminds us that all parties including Mujib had agreed prior to the elections that the constitution would be finalised before the assembly would meet.
*Mujib also did not honour his promise to Yahya Khan that he would modify his Six Points after the elections. He gave public speeches that he would not compromise on the Six Points. Yahya Khan was dismayed by Mujib's public statements and in one meeting said to G W Chowdhury "How could Sheikh Sahab betray me when I have fulfilled all his demands?"
*The military junta had given Yahya a free hand until December 1970 in formulating the transfer of power and holding elections. The junta had a "wait and see" policy. If Yahya could maintain the unity of the country they were fine. But ever since Yahya and Mujib's failed talks in January the military junta was no longer willing to remain passive.
*The election results demonstrated that neither Bhutto nor Mujib represented Pakistan as a whole so there would need to be an understanding between them (as leaders of the two largest elected parties) for the new constitution.
*Bhutto had won the lion's share of West Pakistani seats. He also won in Punjab even though he was a Sindhi. One of the differences between Mujib and Bhutto was their approach to relations with India. Bhutto was more anti-Indian in his approach. While Mujib wanted friendly relations with India.
*When an elderly Bengali politicians suggested to Mujib that Bhutto be made foreign minister in his cabinet, Mujib became angry and to that politician's dismay told him that Bhutto could be made Agricultural Minister but not a Foreign Minister.
*The military junta started favouring Bhutto as they regarded him as a better defender of the country's "national interests." They distrusted Mujib and had never forgotten his role in the Agartala Conspiracy Case. There was also the India factor mentioned above.
*Mujib accused the Army of not wanting to transfer power to him and he started calling Bhutto an Army's puppet. This was a justified accusation.
*Bhutto declared that he was boycotting the upcoming National Assembly meeting and further threatened any West Pakistani politician who would attend it.
*Yahya promised Bhutto that if Mujib was to thrust a "six-point constitution" in the Assembly against the wishes of the West Pakistani members and if Mujib's constitutional draft meant splitting the country, then he would use his Presidential power to immediately cancel the Assembly session. But Bhutto still refused to reverse his decision to boycott the National Assembly meeting.
*So once Yahya Khan decided to postpone the National Assembly meeting, G W Chowdhury wrote Yahya Khan's postponement announcement in "conciliatory" language (which promised that the postponement of the Assembly Session was only a temporary measure) so that there would be minimum provocation in East Pakistan.
*But Bhutto and General Peerzada coerced Yahya Khan to use another draft (without the conciliatory language).
*Following this postponement declaration on 1 March, Mujib and the Awami League revolted and usurped the government's authority in the province.
*While he was running East Pakistan under his parallel government, Mujib still did not officially declare independence even though senior pro-Awami League Bengali officers in the Pakistan Army were offering him a "first strike." He stalled for the final results of his "negotiations."
*At the same time he started calling the province "Bangladesh" and Pakistani flags were torn down, burnt, disrespected and replaced with Bangladeshi flags. Mujib saluted the Bangladeshi flag in a march of Bengali paramilitary units near his residence.
*Mujib was effectively already running the province as a separate country, even if he had not officially declared independence. He issued no less than 31 "Directives" on the administration of Bangladesh.
*Mujib had the loyalty of most of the Bengali soldiers in the East Bengal Regiment and East Pakistan Rifles (units of the Pakistan Army) as well as the province's police. He appointed Colonel Usmani as Commander of the "Revolutionary Forces."
*Meanwhile, Pakistan Army was also trying to fly in troops to East Pakistan (via Sri Lanka, because India had banned flights between the two wings of Pakistan after the incident of plane hijacking by some Kashmiri nationalists).
*Despite his Army Generals getting ready for a confrontation, Yahya Khan still went to East Pakistan in March to talk to and plead with Mujib at a time when East Pakistan was no longer under the government's control but Mujib's.
*Mujib used the Bangladeshi flag over the car he drove in to meet Yahya Khan. He described the President as a "guest" of Bangladesh. There were lots of provocative anti-Pakistan rallies while the negotiations between the leaders took place privately.
*Some foreign diplomats were hinting that there were already established links between Mujib's headquarters in Dacca and Indian officials. Pakistani intelligence services received many such reports.
*While Yahya Khan was making concession after concession to Mujib, the military junta was warning him of the consequences of weakening the national government. The Army Generals had historically distrusted politicians from both West and East Pakistan.
*Bhutto also arrived for talks on March 21.
*On March 22 Mujib told Yahya Khan that the Awami League would not agree to the establishment of any national government, Instead it wanted power to be transferred separately to West and East Pakistan.
*This effectively meant they were demanding that Pakistan be split into two (without explicitly mentioning secession). Yahya Khan pleaded with Mujib to withdraw his demand.
*Yahya was shocked and reminded Mujib that his pledge in 1969 was to transfer power to elected representatives, not preside over the breakup of the country. He warned Mujib that the threat to the country's territorial integrity wouldn't go unchallenged.
*The Awami League rejected Yahya Khan's draft constitution (which gave full autonomy to East Pakistan minus breakup of Pakistan) and promised to present its own draft constitution.
*It seems to G W Chowdhury that the Awami League proposal for splitting the country would now be presented more subtlety in this document deceptively titled "Confederation of Pakistan" so that the failure of the negotiations would not be blamed on the Awami League.
*Mujib and the Awami League knew that this camouflaged proposal for the breakup of Pakistan would be unacceptable to the Army, so they made confrontation inevitable. (i.e. they were trying to provoke the Army to take action and take the blame)
*On 23 March the Awami League presented its draft constitution to Yahya Khan.
*G W Chowdhury read the Awami League's draft constitution. He says that its provisions confirmed that Awami League did not believe in the unity of Pakistan and that the Six Points plan were a veiled scheme of secession after all.
*After 1971, Sheikh Mujib admitted to journalist David Frost in an interview that he had been working for Bangladeshi independence for quite some time.
-End of summary
That said, I have also read in the Bengali academic Dr M Abdul Mumin Chowdhury's book that Mujib was having second thoughts on Bangladesh in March (Gholam Wahed Chowdhury also hints in his book that Mujib was afraid of his radical colleagues in the Awami League) because he knew an independent Bangladesh would be dominated by India that is why he wanted for some time to maintain some link with Pakistan. But it was too late. He had travelled too far with India and his Awami League colleagues. Especially by the time he was released from prison after the war. And because he was afraid of his political rivals in the Awami League such as Tajuddin who were more active during the war while he was in jail, he had to make up for his lack of wartime contribution by making Pakistan look more "brutish" by exaggerating the casualties and atrocities of the war.
As for the start of Operation Searchlight, it was planned to restore the government's writ in East Pakistan and was said to be a pre-emptive action against a Bengali mutiny which the Awami League had planned for 26 March. But the operation was poorly conducted due to the Army acting out of revenge sentiments (for the atrocious treatment they, West Pakistani civilians and Biharis had received in the preceding three weeks at the hands of Bengali nationalists).
There was another operation planned earlier too, in mid-February 1970 to arrest the Awami Leaguers and deploy the military on the streets to prevent any uprising. But there is no evidence atrocities were intended. Hamoodur Rehman Commission Report also concluded the same about Operation Searchlight that atrocities were not an intended part of it.
Sources:
The Last Days of United Pakistan by Gholam Wahed Chowdhury
Wastes of Time by Professor Syed Sajjad Hussain
Behind the Myth of Three Million by Dr M Abdul Mumin Chowdhury