A Sunday civil rights march, January 30, 1972, in Derry, Northern Ireland, ended in British paratroopers fighting marchers. 13 died, 14 were hospitalized, and one died later, but no soldier died. An inquiry found that marchers fired first; a few soldiers later received royal medals.

Disagreement about the rest of the day is so deep 30 years later that a 1998 inquiry continues. In Greengrass' documentary-style film, the complex lead character, Ivan Cooper (Nesbitt) - a Derry civil rights leader, a Protestant, and a nationalist Social Democratic Labor MP - has organized 10,000 marchers, mostly Catholic. Having a Protestant leader shows the depth of division between people citing religion and those who simply want the British out of Northern Ireland.

Cooper is admirable, optimistic, tireless, and fearless. He knows the march has been banned, but expects a peaceful day. As he hands out leaflets, Greengrass cuts in scenes of the army, determined to stop "hooliganism," young man kissing his girlfriend good-bye and promising his mother he'll be fine, and the Derry police chief (McSorley), alarmed by the soldiers, asking if it's wise to ban the march.

Greengrass stunningly records the events. Thousands of extras volunteered, including some 1972 marchers.
From a truck bed, Cooper and other men lead them, and when the march turns away from the soldiers, a few rowdy marchers turn to throw rocks at them. (Pigott-Smith) Maj. Gen. Ford's order of "firm response" is garbled down the chain of command; real bullets replace rubber ones.

Marchers try to halt their few armed compatriots; the British fire first, in cold blood. A wounded marcher is executed by a bullet to his back; another's fate parallels Gerald Donaghey's: Wounded, he's searched twice, then taken by the army, and dies. Soldiers find nail bombs on him "overlooked" by two prior searches; to Greengrass, it's an army attempt to plant evidence to justify the massacre.

Greengrass shows the anti-British factions' anger and the army's smugness after an investigation clears it, inflaming feelings. "Bloody Sunday" is an effective portrayal, and superb filmmaking, its realism enhancing every scene.