PTSD symptoms are a psychological reaction to an experience of life-threatening physical danger or harm. Moral injury is the lasting mental and emotional result of an assault on the conscience — a memory, as one early formulation put it, of “perpetrating, failing to prevent, or bearing witness to acts that transgress deeply held moral beliefs and expectations.”

The idea remains controversial in the military world, but the wars that Americans have fought since 2001 — involving a very different experience of war fighting from that of past generations — have made it increasingly difficult for military culture to cling to its old manhood and warrior myths.