On this day 50 years ago, a platoon of U.S. soldiers entered the hamlet of My Lai in South Vietnam and, in hours, massacred 504 unarmed women, children and old men. Over 300 of the victims were younger than 12; the G.I.s also raped many of the women and burned all the homes. Today, with torturers and warmongers on the rise, the horrors of My Lai serve as a grim warning. In America's wars of choice, says one vet, we are all "one step away from My Lai."