The document summarizes the My Lai massacre that occurred during the Vietnam War. Over 500 Vietnamese civilians were killed by U.S. soldiers over the course of 3 hours. While the massacre was initially covered up, an investigation was later launched after a veteran sent a letter to Congress about the events. Lieutenant William Calley was ultimately the only soldier convicted for the killings, receiving a life sentence though he only served 3 years under house arrest. The massacre increased public opposition to the war and demonstrated the brutality that could occur amid incorrect intelligence and low troop morale.