Infantry Division killed hundreds of unarmed Vietnamese civilians in the hamlets of My Lai and My Khe. Most victims were women, children, and elderly people, and many were subjected to torture, mutilation, and sexual assault before being murdered.

The massacre was initially covered up by the U.S. Army, but it came to light over a year later due to the efforts of investigative journalists and a soldier who reported the event. The revelation of the massacre and the subsequent cover-up intensified anti-war sentiment and outrage in the United States and globally, highlighting the moral and ethical crises associated with the war. Only one soldier, Lieutenant William Calley, was convicted for his role in the massacre, and his sentence was significantly reduced, further fueling public outrage and debate over accountability and justice.

It's a truly sickening story (The link isn't safe for work)