Even though it's been obscured by the horrors of the Yugoslavian civil war and the Palestinian-Israeli conflict, the sectarian violence in Northern Ireland remains among the bloodier chapters of the late 20th century. Most Americans think of "the Troubles" as a vicious circle of Irish Republican Army bombings, British Army crackdowns, and tit-for-tat murders between the province's Catholic minority and Protestant majority. However, there was an earlier phase to the Troubles.

In the late '60s, Catholics staged a series of Martin Luther King Jr.-style civil rights marches to protest discrimination by the Protestant majority. These marches started out peacefully, but started deteriorating into riots after 1968, when British security forces began to harshly suppress them. These crackdowns prompted a resurgence in the IRA's assassination of English soldiers and policemen. Those killings, in turn, spurred the British military to take an even tougher stance against civil demonstrations, which led to more Catholics signing up with the IRA, and so on, with the situation sliding further and further down a slippery slope.

This slope hit its tragic nadir on January 30, 1972, a.k.a. "Bloody Sunday," when 13 Catholic protesters were shot dead by British paratroopers during a march in Derry, Northern Ireland's second-largest city. The event was decried as a massacre by Catholics, but was whitewashed by a London-sponsored inquiry which claimed its troops were returning fire from IRA snipers. But it wasn't until 1997 that Don Mullan's book Eyewitness Bloody Sunday, an exhaustive collection of over 100 firsthand accounts of the day's horror, blew the lid off the official version of events.

Mullan's book is also the basis for Paul Greengrass' film Bloody Sunday. Here, the Northern Irish director has transcended the docu-drama form. The film avoids the pitfalls of dramatization — there's no corny backstory, nor any composite characters. Like the stellar documentary One Day in September, Bloody Sunday grippingly recounts a tragedy that, sadly, could've have been avoided.

The man at the center of that tragedy is Protestant peace activist Ivan Cooper (James Nesbitt, delivering a searing performance), a man who earnestly believes that nonviolence will overcome oppression of his Catholic neighbors. That view is not shared by Major General Ford (Tim Pigott-Smith), the arrogant British military commander whose resolve to crush the protest is superceded only by his faith in his elite paratroopers' skills.

Little does Ford know — or care to know — that the "paras" are itching for a fight; several of their fellow soldiers having been shot the previous month by the IRA, and the survivors are eager for some payback. The commander orders them to exhibit "maximum aggression today — make lots of arrests, pick up at least 200 of the Derry hooligans." This image stands in stark contrast to the majority of the several thousand demonstrators, who are just everyday people; the conflict-shy Cooper even changes the march's route to avoid brushing up against the paras. But a splinter group of protestors pelts the British positions with stones and rocks, then runs back to join the main group. Bursting out of their armored cars, the paras come after the stone-throwers with their weapons locked, loaded, and ready to be fired.

Viewers will be thunderstruck by what happens next. Indeed, Bloody Sunday's horrific climax is so powerful that some critics have accused the film of being pro-Republican propaganda. But even though Greengrass has long covered the Troubles — he was the first filmmaker allowed inside Belfast's infamous Maze Prison — his presentation is surprisingly evenhanded, showing frustration and recklessness on both sides. The big difference is one side didn't have Enfield assault rifles, although several IRA infiltrators in the crowd are shown taking pot-shots with pistols.

Using innovative editing and ultra-verité camerawork, Greengrass also ratchets up the tension to almost unbearable levels. Few films have captured the chaos of an urban conflagration with such fury, and audience members will leave feeling as shaken as Nesbitt's Cooper looks when the bullets stop flying. With his hangdog features looking more sullen than should be humanly possible, he prophetically tells reporters that "The British army couldn't have handed the IRA a bigger victory than they did here today." Sadly, the next 25 years of bloodshed proved him right.