In 1970, the year he began shooting pictures, Gilles Peress was sent to Northern Ireland by his photo agency, Magnum. “They told me, Hurry up, there’s going to be trouble. But the trip was a fiasco. There were no riots, and I got no pictures.” Still, Peress kept going back, and in 1972 he photographed a Catholic civil rights march that ended with a massacre by British paratroopers of thirteen unarmed civilians. That was Bloody Sunday, the start of the period known as the Troubles. Peress returned to Northern Ireland almost every year. The extraordinary compression of the human drama in what he calls a “theater of passion” inspired him to document in black and white very aspect of existence. He organized his photographs in chapters constructed as days—some composite, some real—and in 1994, when the IRA declared a cease-fire, he went back for one last chapter: A Day of Peace. To see Belfast afresh, he began shooting in color. That trip led to several others, and to the pictures that follow. “It became a very long day,” Peress says. “As usual, peace and peacemaking in their meanderings are more murky than war.”