On Killing: The Psychological Cost of Learning to Kill in War and SocietyThe revised and updated edition of Lt. Col. Dave Grossman's modern classic about the psychology of combat was hailed by the Washington Post as "an illuminating account of how soldiers learn to kill and how they live with the experiences of having killed." In World War II, only 15 to 20 percent of combat infantry were willing to fire their rifles. In Korea, about 50 percent. In Vietnam, the figure rose to more than 90 percent. The good news is that