The My Lai Massacre was an atrocity that was committed during the Vietnam War. It happened in March of 1968. The soldiers who committed this atrocity were Americans.
The only person who was actually convicted of and punished for participating in the My Lai Massacre was Lt. William Calley. He was the commander of the platoon that committed the atrocity.
In this atrocity, hundreds of Vietnamese civilians were killed. Many of them were attacked in other ways. There were, for example, rapes as well as evidence of beating and torture.
This atrocity helped to turn public opinion in the US even further against the war.
On March 16, 1968 the angry and frustrated men of Charlie Company, 11th Brigade, Americal Division entered the Vietnamese village of My Lai. "This is what you've been waiting for -- search and destroy -- and you've got it," said their superior officers. A short time later the killing began. When news of the atrocities surfaced, it sent shockwaves through the U.S. political establishment, the military's chain of command, and an already divided American public.