The body of the Iraqi prisoner was found naked and badly bruised in 2003, outside a detention center in southern Iraq run by United States Marines. The 52-year-old man had been beaten, deprived of sleep, forced to stand for long periods and interrogated by Marines about his alleged role in a fatal ambush of American forces.

James N. Mattis, President-elect Donald J. Trump’s nominee for secretary of defense, was then a major general and the commander of the Marine division in Iraq responsible for the center. He quickly convened an inquiry into the death, which led to courts-martial, and banned the harsh techniques used at the prison.

“General Mattis was all up in arms over this,” Ralph Dengler, then a lieutenant colonel, testified at a military hearing in January 2004. He added that the commander, who arrived hours after the discovery on a planned visit with his British counterpart, had immediately described the death as “the worst thing that happened” under his watch in the Iraq war.

“I was surprised that he would have felt that strongly about it, considering many of the other deaths, including American deaths,” Colonel Dengler said.