William Calley was charged with six specifications of premeditated murder related to the My Lai Massacre, a mass killing of between 347 to 504 unarmed South Vietnamese civilians on March 16, 1968, by U.S. Army soldiers. My Lai, located in Quang Ngai Province, witnessed one of the darkest chapters of the Vietnam War when American troops, part of the My Lai Task Force, conducted a search-and-destroy mission under the pretense of combating Viet Cong insurgents. Instead, troops committed atrocities, including mass executions, rapes, and the destruction of homes. Lieutenant Calley, as the commanding officer of Charlie Company, was one of the key figures, whose orders and actions during the event were heavily scrutinized and questioned by military law.

In the aftermath, the My Lai Massacre became emblematic of the moral and ethical controversies surrounding American military engagement in Vietnam, starkly contrasting the stated objectives of the war with the reality on the ground. The public outrage that followed, fueled by shocking photographs and eyewitness accounts, significantly impacted American sentiment towards the Vietnam War and military conduct, leading to broader anti-war demonstrations across the United States.

Calley’s trial began in 1970 and turned into a flashpoint for debates on military accountability, the role of leadership, and the complexities of warfare. His conviction, initial sentence, and eventual parole sparked public discourse on justice and the responsibilities of soldiers in combat zones, especially in scenarios requiring moral judgment under the pressures of war.