In Northern Ireland, debate is raging about what exactly happened 25 years ago when a group of Catholic marchers walked into a hail of bullets from British troops.
No anniversary casts a longer shadow over the modern politics of the province of Northern Ireland than Jan. 30, 1972 - so-called Bloody Sunday.
Last weekend, an estimated 20,000 Catholics in Londonderry, Northern Ireland's second largest city, paraded to commemorate their 14 unarmed co-religionists killed in the shooting.
Instead of laying passions to rest, as the British government had hoped, the march has fueled demands for a new investigation into why the troops opened fire and who was responsible for the killings.
The demand is coming not only from the province's minority Catholics, but from the government of the Republic of Ireland. Irish Prime Minister John Bruton claims he has "fresh evidence" he wants to present to his British counterpart, John Major.
But Mr. Major, who has seen the Northern Ireland peace process slowly disintegrate over the past year, is resisting Mr. Bruton's call. Major's officials say a new inquiry now might worsen already tense relations between Catholics and Protestants and could destroy the peace process completely.
On Bloody Sunday, says Irish historian Sabine Wichert, between 2,000 and 5,000 people in mainly Catholic Londonderry held a civil rights protest march, in defiance of a ban on demonstrations.
When the troops attempted to halt the march, Ms. Wichert says, they thought they were being shot at by snipers and fired more than 100 rounds of ammunition into the advancing crowd. All the dead civilians were later found to have been unarmed.
An official inquest at the time called the shootings "sheer unadulterated murder." An inquiry set up by the British government found that some British soldiers had acted recklessly, but failed to condemn the Army or the authorities in Belfast and London. Ever since, the Irish Republican Army has portrayed the 14 killed on Bloody Sunday as nationalist martyrs.
Gerry Adams, president of the IRA's political wing, Bruton, and others calling for a new inquiry base their demands on evidence presented in a new book, "Eye Witness, Bloody Sunday," by Don Mullan, an Irish human rights activist.
Mr. Mullan's work, the product of years of research, has sparked several television news reports and documentaries. These allege that the 14 marchers were killed not by British paratroopers who confronted them in the street, but by British snipers positioned on Londonderry's high city wall.
Mullan cites the testimony of medical experts who say the bullets which killed the marchers produced wounds that could not have been caused by gunfire at ground level. The experts say the wounds were consistent with bullets being fired from the wall.
This evidence has raised the possibility that when British troops said they thought they had been fired on, they had actually heard gunfire from their own snipers.
Major's reluctance to hold a new inquiry is understandable. In the House of Commons, he is dependent on the votes of Ulster Unionist, and therefore Protestant, members of Parliament to sustain his governing majority. David Trimble, leader of the official Ulster Unionist Party, says he can see "little point" in a new investigation.
Other unionist politicians are more sympathetic. Gregory Campbell, leader of the Democratic Unionist Party in Londonderry, says: "Quite obviously the British paratroopers took action they ought not to have taken, and innocent people died."
The debate in Northern Ireland itself is prompting discussion on the British mainland about what could or should be done to meet the claims of those who say what really happened on Bloody Sunday deserves an act of either contrition - or at least attrition - on the part of Britain.
London's Guardian newspaper on Monday, in an editorial headed "Unfinished business," said Mullan's allegations "deserve a detailed point-by-point response."
"Liberal politicians who want to foster a just and progressive approach to Northern Ireland could do far worse than admit publicly that Bloody Sunday remains a shameful stain on the reputation of this country," the paper said.
It added that if Labour opposition leader Tony Blair wins the coming general election he should "acknowledge collective responsibility for the events of 1972" and invite others to repudiate "a past for which all share some blame for atrocity."