On March 16, 1968, in the wake of the Tet Offensive, American soldiers committed perhaps the most brutal, and certainly the most infamous, atrocity of the Vietnam War. The tragedy occurred in My Lai 4—one of several hamlets in Song My village in Quang Ngai province, a historic stronghold of the National Liberation Front. During an uneventful search-and-destroy mission, members of Charlie Company, First Battalion, 20th Infantry Division, commanded by Lieutenant William Calley Jr., massacred from 300 to 500 unarmed, unresisting Vietnamese women, children, and elderly men. They raped, sodomized, and mutilated many of their victims. Once the full story of My Lai reached the American public, it reshaped how they viewed the war, and, in no small way, how they understood their own hallowed history. My Lai seared America's collective memory with seemingly indisputable proof that American behavior often failed to live up to its self-righteous rhetoric...