‘Hossain took his six-year-old son with him to the protest, holding a banner with the message, “Razakars [Islamist collaborators] must be hanged.” The child carried a toy gun. ‘My uncle was killed in 1971 by the Pakistan army,’ Hossain said. ‘I cannot forgive those who killed and stood with the killers.’

Hossain, a 45-year-old banker, had never been to a demonstration before, the Observer noted, but here he was taking his small child to a mass protest in Dhaka’s Shahbag Square calling for those who collaborated with West Pakistan forces during the war of independence-some of the country’s leading politicians-to be put to death. The increasing polarisation within Bangladesh broadly mirrors the split between the two main political blocs, the Awami League and the Bangladesh National Party (BNP). But it is about more than differing visions of the country’s future: it is as much a battle over the past.

Shahbag quickly acquired the symbolism of Dhaka’s Tahrir Square. The spark that set the protests in motion, which have seen up to 500,000 ordinary Bangladeshis mass there, appears to have been a V-for-victory sign flashed at supporters by Abdul Quader Mollah, assistant secretary-general of Jamaat-e-Islami, Bangladesh’s largest Islamist party and BNP ally, as he left the war crimes tribunal. Mollah, the ‘Butcher of Mirpur’, had just been convicted of beheading a poet, raping an 11-year-old girl and shooting 344 people in 1971. That V sign was a gesture of contempt for the long-overdue reckoning for war crimes, Bangladesh’s Nuremberg. And it stemmed from the awareness that if, or perhaps when, the BNP returned to power, Mollah and his fellow collaborators would almost certainly be freed.

The demonstrations began on February 5 and, propelled by Facebook, Twitter and bloggers, quickly became the country’s biggest protest in 20 years. The galvanising effect of the movement quickly spread around Bangladesh and abroad, not least to London, where Jamaat supporters have been accused of stoning Shahbag protesters. It has also been notable for the prominent role of women at the protest.

The writer Nick Cohen called Shahbag: ‘A grassroots uprising for the most essential and neglected values of our age: secularism, the protection of minorities from persecution and the removal of theocratic thugs from the private lives and public arguments of 21st-century citizens.’ Leading writers, former freedom fighters and the Bangladesh cricket team went to Shahbag Square to lend their support. Largely dismissed and ignored, though, were politicians of every hue who came to speak. Hana Shams Ahmed, writing in the Bangladeshi Daily Star, said: ‘It is not only the BNP [the] Awami League too has forged alliances with Jamaat in the past [for] political gains.’

This role of ‘kingmaker’ in Bangladeshi politics is perhaps surprising considering the party was opposed to the very existence of an independent Bangladesh but as Tahmima Anam, a Bangladeshi writer, noted: ‘Though the Jamaat party only won two out of 300 seats in the last election, their presence as a powerful third party in politics has remained unquestioned-until now.’

Only one of the 11 on trial with Mollah is not a member of Jamaat-e-Islami. Another of the Jamaat accused, Abul Kalam ‘Bachchu’ Azad, who is believed to have fled to Pakistan, was sentenced to death in absentia for crimes against humanity four decades ago. A cleric and a presenter of Islamic TV programmes, he was convicted of shooting dead Hindu civilians, raping Hindu women during the war, arson and forced conversion. The leader of Jamaat, Delwar Hossain Sayeedi, was also sentenced to death for war crimes, including murder and rape.

Within weeks, President Zillur Rahman had signed into law an amendment to the war crimes tribunal statute allowing prosecutors to seek stiffer sentences on appeal and to charge organisations with war crimes, both key Shahbag demands. In this, the Shahbag protests differ from Tahrir Square, where demonstrators wanted nothing less than the overthrow of the ancien régime. Protesters, according to the Economist, argue ‘their movement is a narrow one against political Islam: in favour of secular government, they want Jamaat banned. A rampage by Jamaat’s violent youth wing has done nothing to damp down such calls.’

Although some of its supporters had joined the protests in Shahbag, which has now been dubbed ‘new-generation roundabout’, Jamaat responded by calling general strikes, and then detonating homemade bombs and setting fire to vehicles (it keeps people off the streets and thus makes a success of the strike). Soldiers were deployed after four days of rioting and 100 people were reported killed; police detained more than 150 opposition leaders and activists.

As the Bangladeshi journalist Zafar Sobhan noted, citing the disappearance of BNP activists under the current government and, when the BNP was in power from 2001-06, the assassination of two leaders of the then-opposition Awami League and a 2004 grenade attack on an AL rally aimed at killing the entire leadership, which left 23 dead: ‘Politics in Bangladesh is a blood sport, and neither the ruling AL [Awami League] nor the opposition BNP has clean hands.’

The seesaw of Bangladesh’s two-party politics has much to do with the contested view of the country’s painful birth. According to the International Crimes Tribunal, the inapt name for the purely local war crimes trial: ‘Some three million people were killed, nearly quarter [of a] million women were raped and over 10 million people were forced to take refuge in India to escape brutal persecution.’

The numbers matter. What is now seen as genocide was vastly downplayed originally: the official Pakistani estimates were 26,000 dead and 2,000,000 refugees. An Oxford historian, ‘whose methodology was savagely criticised’ according to Philip Hensher in the Independent, put the figure at 50,000-100,000 dead from all sides in the war. A similarly conservative study by the Peace Research Institute in Norway and Sweden’s Uppsala University in Sweden estimated that 58,000 people died.

However, Hensher quotes the Pakistani president, General Yahya Khan, as saying in 22 February 1971: ‘Kill three million of them, and the rest will eat out of our hands.’ The following month, the Pakistani army launched Operation Searchlight and with it the massacre of intellectuals, doctors, academics, students and other secular nationalists who wanted their country to break away from rule by Islamabad.

Rudolph Rummel, an American political scientist, believed the ‘final estimate of Pakistan’s democide [a word he coined for mass murder by governments] to be 300,000 to 3,000,000, or a prudent 1,500,000.’ (Others to suffer included Christians and Hindus at the hands of Pakistani forces and their collaborators, and Urdu-speaking Biharis by Bengalis).

‘It is thought that at least 200,000 women were raped by the Pakistani forces and their collaborators-25,000 victims found themselves pregnant, so that is not implausible,’ said Hensher, adding: ‘Out of thousands of episodes, one should read the evidence to this trial given by an extraordinarily brave woman, the single survivor of her family. She told how she saw her parents, her two sisters and two-year-old brother killed in front of her before 12 soldiers raped her. She was 13 years old.’

Why did it take 41 years to secure a conviction for these crimes? According to David Bergman, the journalist behind a 1995 Channel 4 documentary on Bangladeshi war crimes suspects living in Europe, Pakistan blocked initial attempts after independence by what was little more than hostage taking. In his blog Bangladesh War Crimes Tribunal, Bergman says India freed 92,000 Pakistani prisoners of war and civilians in 1972 but 195 military officers, whom the Bangladeshi government wanted to prosecute, remained in Indian custody. However, Pakistan also detained 206 Bengalis whom they said they would prosecute for passing on secret information.

Perhaps equally importantly at the time was the fact that making Pakistani officers and Bangladeshi Islamists face justice was not considered helpful to US interests in the region by President Nixon and his secretary of state, Henry Kissinger, who saw Islamabad as a counterweight to Soviet-aligned India and as a conduit for their rapprochement with Mao’s China.

In April 1971, 20 officials of the US consulate general in Dhaka, supported by the consul-general, Archer Blood, sent a telegram of protest at the killings. The so-called Blood telegram, one of the most famous examples of dissent within the US government, declared of the actions of the invading army and its collaborators: ‘Unfortunately the overworked term genocide is applicable.’

The grim realpolitik of how the Nixon administration ignored this plea for action and focused instead on thwarting India’s intervention in the Bangladesh war (after millions of refugees had streamed over its border) can be followed in the US state department archives. Far from trying to halt the mass murder, Washington sent its seventh fleet to support Pakistan, backed by a British naval group. As Rossiyskaya Gazeta said: ‘This was perhaps one of the most ironic events in modern history, where the western world’s two leading democracies were threatening the world’s largest democracy in order to protect the perpetrators of the largest genocide since the Holocaust in Nazi Germany.’

There have been many criticisms of how fair the procedures of war crimes tribunal have been, and condemnation of the abduction of a defence witness from among others the International Bar Association, Human Rights Watch, Bergman and the barrister Lord Carlile.

As far back as December, the Economist was questioning the objectivity of Mohammed Nizamul Huq, the supreme court judge presiding over the tribunal. He later resigned. It wrote at the time: ‘The emails and phone conversations we have seen suggests the government tried to put pressure on Mr Nizamul, albeit he seems to have resisted it. It seems to show he worked improperly with a lawyer based in Brussels, and that the lawyer co-operated with the prosecution-raising questions about conflicts of interest.’

Human Rights Watch said: ‘Bangladesh’s overall human rights situation worsened in 2012 Flawed trials against those accused of war crimes in the 1971 war for independence continued, despite calls by the US war crimes ambassador, Stephen Rapp, and several international groups to amend the International Crimes Tribunal Act [which retrospectively allowed stiffer sentences to be sought] to ensure it complied with international fair trial standards.’

‘A government supposedly guided by the rule of law cannot simply pass retroactive laws to overrule court decisions when it doesn’t like them,’ HRW said, also criticising the tribunal for allowing prosecution witnesses’ statements as evidence without live testimony being heard, and dismissed the prosecution’s claim that witnesses were unavailable as untrue.

To put these criticisms in context, one reader commenting on the Economist’s coverage criticised the drive for objectivity as ‘a little silly’. Many Bangladeshis were aware of the flaws in the trials, the reader said, but ‘many overlook these flaws because of the scale of Molla[h’s] crimes For us, we’ve just put Hitler on trial.’

If justice delayed is justice denied then the war crimes tribunal is undoubtedly overdue and welcome, but one has to ask whether the mass thirst for vengeance against the Islamist collaborators is itself storing up problems for the future-and whether due process and the right to a fair trial are being lost in the rush for retribution.