Charlie Company had been in Vietnam since December 1967. Three months of booby traps and mines had killed or wounded twenty-eight of their number without a single direct engagement with the enemy. Frustration and fear had become indistinguishable. Intelligence placed the Viet Cong 48th Local Force Battalion in Son My village, and Task Force Barker was assembled to destroy it. The area was designated a free-fire zone. On the eve of the assault, Captain Ernest Medina briefed his men: nearly all civilians would have left for market by seven in the morning, and anyone remaining was likely Viet Cong or a sympathizer. When asked whether the orders included killing women and children, accounts of Medina's response differed, though several soldiers testified they understood the instruction as total destruction. One defense witness later recalled Medina ordering them to destroy everything "walking, crawling, or growling." Rifleman Varnado Simpson remembered it simply: "We were told to leave nothing standing."

The helicopters touched down at 7:30 a.m. after a short artillery barrage. First Platoon, led by Second Lieutenant William Calley, and Second Platoon entered the hamlet in line formation, firing at figures in the rice fields as they approached. Instead of the expected enemy battalion, they found a village waking up to an ordinary morning. The killing was systematic. A group of seventy to eighty villagers was herded to an irrigation ditch and executed on Calley's repeated orders. Women tried to shield their children with their bodies; when the adults fell, Calley shot the children who stood up. Another group of twenty to fifty people was marched to a dirt road and killed there. Second Platoon swept through the northern half and the sub-hamlet of Binh Tay, killing at least sixty to seventy more. Third Platoon was sent in afterward to deal with any "remaining resistance." At eleven o'clock, Medina radioed a cease-fire. First Platoon took a lunch break. The Peers Commission later documented that at least twenty women and girls, some as young as ten, were raped during the assault. Three weapons were recovered from the entire village.

Warrant Officer Hugh Thompson was flying reconnaissance above Son My when he began noticing bodies -- civilians, not combatants -- scattered across the village. He landed his helicopter beside a ditch full of wounded and dead villagers and asked a lieutenant if he could help evacuate the survivors. The response, as Thompson later testified, was that "a hand grenade was the only available means of evacuation." Thompson spotted a group of civilians being herded toward a bunker by ground troops. He landed again and told his crew chief, Glenn Andreotta, and door gunner, Lawrence Colburn, that if the soldiers fired on the villagers while he tried to get them out, they were to open fire on the American soldiers. Thompson then positioned himself between the troops and the civilians and called in helicopter gunships to evacuate the survivors. Andreotta climbed into a ditch and pulled out a bloodied but unharmed four-year-old girl. Thompson reported what he had seen using words like "murder" and "needless and unnecessary killings." He was initially awarded a Distinguished Flying Cross with a fabricated citation about rescuing civilians from "intense crossfire." He threw the medal away. Thirty years later, the Army replaced it with a Soldier's Medal -- this time with an honest citation.

The Army reported the operation as a victory: 128 Viet Cong killed in a fierce firefight. General Westmoreland sent congratulations. Stars and Stripes ran the headline "U.S. Troops Surround Red, Kill 128." Colonel Oran Henderson investigated Thompson's allegations and concluded that roughly twenty civilians had died accidentally from artillery fire. The wall of silence held for over a year, until Ronald Ridenhour, a soldier who had heard eyewitness accounts from Charlie Company members, wrote letters to thirty members of Congress, the Secretary of Defense, and the Chairman of the Joint Chiefs. Most ignored him. Congressman Mo Udall did not. Investigative journalist Seymour Hersh tracked the story and tried to sell it to Life and Look magazines. Both declined. Hersh went to the small Dispatch News Service, which sent it to fifty newspapers; thirty published it on November 13, 1969. A week later, Army photographer Ronald Haeberle's color photographs appeared in the Cleveland Plain Dealer -- images of old men, women, and children lying dead in ditches and on roads. "They're pretty terrible," Defense Secretary Melvin Laird told Henry Kissinger. "There are so many kids just laying there." The photographs, Laird admitted, made it impossible to sweep the story under the rug.

Twenty-six soldiers were eventually charged with criminal offenses. Only one was convicted. Lieutenant Calley was found guilty of murdering not fewer than twenty-two villagers and sentenced to life in prison. Two days later, President Nixon ordered him transferred to house arrest. His sentence was reduced to twenty years, then further. He served three and a half years under house arrest at Fort Benning, including three months in a disciplinary barracks, before being paroled in September 1974. Captain Medina was acquitted after denying he had given the orders, though he later admitted he had suppressed evidence and lied about the civilian death toll. The brigade commander, Colonel Henderson, was acquitted. Division commander Major General Koster was demoted and stripped of a Distinguished Service Medal. No one was charged with rape. In August 2009, Calley made his only public apology, at a Kiwanis Club meeting in Columbus, Georgia. Tran Van Duc, who was seven years old at My Lai on the day of the massacre, called the apology "terse" and wrote Calley a public letter reminding him that time did not ease the pain. The memorial at Son My today lists all 504 names. The Vietnamese call it the Son My massacre, because My Lai was only one of the hamlets where the killing took place.