When James Nachtwey graduated from Dartmouth in 1970, he didn't have a career mapped out. So he traveled around the world. Perhaps because the bloodshed in Vietnam was at its height, he became fascinated with war. He taught himself photography and spent hours staring at scenes of conflict in art books and at exhibitions. "Those pictures had the greatest emotional impact on me," Nachtwey recalls. "It seemed to me the most worthwhile thing one could do with a camera."
In 1980 Nachtwey quit his job as a photographer for a New Mexico newspaper and went to Northern Ireland. Since then he...