Lieutenant William Calley was the only American officer convicted for his actions during the My Lai Massacre, where more than 500 unarmed Vietnamese civilians were killed over the course of several hours. The attack occurred on March 16, 1968, by soldiers from Charlie Company during the Vietnam War, maximizing the tragedy of the event. Although reports of the massacre emerged shortly after, it wasn't until investigative journalist Seymour Hersh's reporting in late 1969 that the incident received widespread attention, igniting major public outcry and debate about the U.S. military's conduct in Vietnam.

Calley was charged with premeditated murder in 1970, and his trial began in 1971. This high-profile court-martial was held in Fort Benning, Georgia, and became a focal point for national discourse on military ethics and the morality of the Vietnam War. The trial produced intense reactions both in support of and against Calley; some saw him as a scapegoat for failures in military policy while others believed he should be held accountable for his actions. Ultimately, Calley was found guilty and sentenced to life in prison, although he served only three years under house arrest before being released.

The exposure of the My Lai Massacre and Calley's conviction crystallized the anti-war sentiment growing in the United States at that time. This event highlighted issues surrounding military protocols, rules of engagement, and the psychological impact of warfare on soldiers. It also raised profound ethical questions about the conduct of U.S. forces and their treatment of civilians during conflict.