January 30, 1972, later known as Bloody Sunday, was a turning point in history before it became a hit song by U2. In defiance of a ban imposed by the British military presence, thousands protested in Derry in a non-violent march against internment without trial and other unjust policies. By the end of the day, members of the 1st Battalion Parachute Regiment had shot 27 demonstrators, 13 fatally.

Who started the shooting? Were the Paras fired upon first, or did they shoot indiscriminately and without provocation and murder innocent people? Was this violence the result of incompetence or a sinister design? Paul Greengrass’s uncompromising, brutally moving Bloody Sunday doesn’t try to answer those questions, though its convictions are clear. It is adamant that the massacre ended any hope of a peaceful resolution of the Northern Ireland conflict, ushering in almost 30 years of sectarian warfare. More important, though, is the way Bloody Sunday transforms the chaos of events into the transcendence of art, elevating a partisan atrocity into a universal tragedy.

In short, Greengrass doesn’t make it easy on anybody, least of all those having a hard time with Ulster or cockney accents (call me a wimp, but I could have used subtitles). His source material is especially daunting: Don Mullan’s Eyewitness Bloody Sunday compiles the testimony of scores of witnesses to the massacre, accounts originally solicited by Northern Ireland civil-rights organizations to present to a British inquiry into the incident (the Widgery Tribunal ignored the material and ultimately exonerated the British).

The book makes electrifying if depressingly repetitive reading, but Greengrass conveys the immediacy and the turmoil of the original through an assaultive but oddly elegiac narrative. Brief fragments, shot in hand-held 16mm and separated by blackouts, collide in an Eisensteinian montage while allowing a Brechtian reflectiveness. In other words, the film hits you over the head and then gives you a moment to think.

Under this seeming onslaught is a calculated, symmetrical structure. Greengrass has reduced the book’s multitude of points of view to four representative characters. Ivan Cooper (James Nesbitt), the Protestant MP representing the Catholic neighborhoods of Derry, is the naive but determined leader of the marchers, a genial, Gandhian glad-hander who is soon in over his head. His counterpart on the British side is Brigadier Patrick MacClellan (Nicholas Farrell), a seasoned soldier torn between his own desire to use restraint and the pressure for a crackdown from those above. Caught up in the ranks are Gerry Donaghy (Declan Duddy), a 17-year-old "hooligan" with Fenian inclinations and a Protestant girlfriend, and Soldier 027 (Mike Edwards), a young Para who’ll soon learn the difference between decency and loyalty.

Inevitably, the four narrative lines crash and entangle, as the marchers gather and the Paras prepare and their movements are charted on a map in British headquarters. As the screen explodes in sudden and incomprehensible violence, the segments lengthen, until a climactic scene in an abattoir-like hospital filled with the dead, the dying, and the bereft seems to go on forever. The effect is not so much outrage as it is grief, not anger but awe. It’s like surviving a disaster and attaining an awful clarity.

That clarity, though, is not fully sustained. There is a fifth character in the film, the smug and treacherous British Major General Ford (Tim Pigott-Smith), and he becomes by default the villain of the piece. Neither is there an equivalent on the Irish side, only a sullen IRA man in a car who gives Cooper a hard time and then more or less withdraws. Also, Greengrass tries a little too hard to personalize his characters; a squabble between Cooper and his girlfriend just before the catastrophe in particular seems gratuitous, if not trivializing. So those who dismiss the film as propaganda might have a point, as do those who question the whole notion of portraying historical truth through movie fiction.

On the other hand, was Yeats’s "Easter 1916" propaganda? Was it true? Like that great poem, this film ends with the naming of names; then there’s a close-up of Nesbitt’s face. The culmination of one of the year’s best performances, it is a reminder that the terrible beauty has been born yet again.