The tradition of honor has largely disappeared from modern discourse with the exception of military life. In that world, separated from civilian conventions, this ancient, once practically universal, code of behavior still reigns. No army, past or present, has long survived without a disciplined sense of hierarchy under orders, an ideal of valor under battle stress, and an intense bonding of warriors under arms. For those at war, faith in the ethic helps to reduce a sense of vulnerable isolation and fear of dying alone and unmourned. With all its qualities of discipline and heroic bearing, though, honor's relationship to violence is undeniable. Thanks in part to films including Gone with the Wind, the popularity of Civil War reenactments, and neoconservative Rebel flag waving, nostalgia for the romance of heroism and cavalier manners persists in public memory. Honor also has long had a merciless side, however, that is not always...