We need to consider the details of the speech carefully because it is open to misinterpretation - partly because Sheikh Mujib deliberately introduced constructive ambiguities into it. He recalled the suffering caused by earlier military actions by saying: "The history of Bangla is the history of the staining of streets with the blood of the People of this country". He then said "…the struggle this time us for our independence" - and at the end of the speech, he repeated that line twice, resoundingly.
But, flexible as ever, he shrewdly stopped short of a unilateral declaration of independence, even though he was under pressure to do just that from radicals who were an important force within his Awami League. He avoided such a declaration for two reasons. First, he had been informed that if he declared independence, the Pakistani air force had orders to bomb the meeting - where hundreds of thousands of people had gathered - and the commander of Pakistan's 9th division had told senior Awami League leaders that he would immediately take military action on the ground.
Second, Sheikh Mujib wanted to leave the open the possibility of talks to produce an agreement that would avoid widespread violence while meeting Bangali demands for autonomy. In his speech, he addressed the Pakistani armed forces by saying "…you are my brothers… Do not make this country a hell and destroy it" (repeated twice). "If we can solve things in a peaceful manner, we can at least live as brothers."
Two leading political analysts in Bangladesh today argue, correctly in my view, that the speech was a master stroke not because it was a declaration of independence - it was not - but because it was ambiguous. It left the door open for discussions that might avoid massive bloodshed.
Between his speech on 7 March and the 23rd, Sheikh Mujib participated in extensive discussions with the most senior West Pakistani leaders. But the latter did not negotiate in good faith. They even went to the extent of signalling, on 24 March, that an agreement with Sheikh Mujib had been reached. But that was a lie. In reality, they used the period when they were talking to build up their armed forces in East Pakistan. They were preparing for a military crackdown - which began the day after they falsely indicated that a deal has been achieved.
Their real intentions had become clear to Awami League leaders who had an effective intelligence network in the days before 25 March. As a result, Sheikh Mujib urged other senior Awami League leaders to go into hiding. But when the army took to the streets on the night of 25-26 March, he remained in his house awaiting arrest - at great risk to himself. The explanation for his decision is a topic of debate.
Some argue that he was confused and "had no plan whatsoever". But it appears clear that - as he himself later said -- he offered himself for arrest in order to minimize death and destruction. He calculated that the military would find it impossible to subdue the Bangalis - a plausible idea at the time, given the near-total response to his call for non-cooperation, which later turned out to be true. He reckoned that if that happened, West Pakistani leaders would need someone close at hand to negotiate with.
But he was also prepared to pay with his life. As he said at the time, "Yahya (the Pakistani military ruler) thinks that he can crush the movement by killing me. But he is mistaken. An independent Bangladesh will be built on my grave".
He was arrested at his home in early hours of 26 March, and flown to Pakistan later that day, where he was held prisoner. Instead of negotiating with him, the West Pakistani authorities tried him for treason and sentenced him to death.
In East Pakistan (or Bangladesh), the West Pakistani armed forces unleashed a brutal campaign to subdue the Bangalis. They committed massacres of Bangali police, Bangali soldiers who had left the army to resist, students, intellectuals and other civilians. Many consider this to be an act of genocide.
But the resistance could not be overcome, and a bloody civil war unfolded over the next nine months in which Bangali insurgents more than held their own. On 3 December 1971, the Indian army joined the struggle. Thirteen days later, the Pakistani army surrendered to Bangladeshi and Indian forces - and a new nation emerged.
The death sentence on Sheikh Mujib was never carried out. On 8 January 1972, he was released. He flew home via London and Delhi, and arrived in Dhaka on 10 January 1972 - to take up the leadership of Bangladesh. Later in 1972, he introduced a new democratic constitution, and the next year his Awami League won a landslide election victory.
But Bangladesh had been ravaged by war. Many leading Bangalis who might have helped rebuild the country had been slaughtered. There were major problems reviving the economy, and restoring law and order. On 15 August 1975, discontented soldiers staged a coup and murdered Sheikh Mujib and 16 members of his family, including children. Only two of his children were absent and survived - one of whom, Sheikh Hasina Wajid, is prime minister of Bangladesh today. Three months later, two more coups followed, and Bangladesh remained under military rule until 1991 -- a sad end to this story of a remarkable struggle, led by a remarkable man.
This account of the grim struggle by the Bangalis and Sheikh Mujib, plus certain other things, remind us of how important it is that this country be studied. What are those 'other things'? The brutal 1971 Pakistani crackdown killed many people who might have served as capable government officials after Bangladesh came into being. And then after 1975, the country suffered a quarter-century of inept military rule, which reminded us yet again that armies are hopeless at governing complex Asian societies. As a result, it has been difficult for governments in Bangladesh, even after democracy was restored after 1991, to achieve great things.
But in spite of all that - and in part because of it -- Bangladesh has developed some of the most constructive non-governmental organisations on earth, to compensate for the limitations of government institutions. BRAC, the Grameen Bank and many other civic associations add up to a more formidable set of civil society organisations that we find in almost any other country in Asia, Africa or Latin America.
Those organisations, together with the government, have accomplished a great deal. For example, Bangladesh has done better than India - which has superior human and financial resources - in promoting family planning and in tackling malnutrition. The implications in human terms are startling, as a brief comment on one detail will show. In 2014, 39 percent on Indian children under five were so malnourished that they suffered 'stunting' -- their bodies and brains did not develop fully.
And the damage was irreparable. In other words, a huge proportion of young Indians are less intelligent than they would have been had they received adequate nutrition. That is a grotesque injustice and - to put it in terms which Indian leaders might understand - an appalling waste of a vital national resource. Bangladesh can take great credit for doing better.
It is also important to note that while Bangladesh is a vast, overwhelmingly Muslim country, it has coped reasonably well with Islamic extremism. And it has sustained democratic politics since 1991. Those of us who study South Asia often focus on its gigantic neighbour, India - for understandable reasons. But Bangladesh is not just a huge country in its own right, but an extremely important country. We need to pay it the attention it deserves. (Concluded)
The writer is with the Institute of Commonwealth Studies, London