On March 16, 1968, American soldiers from Charlie Company were angry about Viet Cong booby traps, frustrated by recent casualties, and still shaken by the Tet Offensive. They took these resentments out on the residents of two hamlets, slaughtering around 500 unarmed women, children, and elderly people in what is known today as the My Lai massacre.

Whether Capt. Ernest Medina directly ordered his men to kill civilians is doubtful, but he certainly let it happen for hours without intervention. This was no short firefight: It was an extended series of rapes and murders. About half the soldiers participated; about half stood aside and refused to actively participate. But hardly anyone tried to help the victims.

The exceptions—the morsels of humanity—were three men in a helicopter: Hugh Thompson, 25; Lawrence Coburn, 18; and Glenn Andreotta, 20. Given their aerial view of things, the crew was baffled by the number of bodies they were seeing. None of the dead appeared to be armed, or to be even males of soldier age. Twice the crew landed, marked injured civilians for aid, and returned to find them dead. Colburn said later that Medina was the one who killed a woman they had attempted to help.

All this enraged Thompson, the pilot, though by all accounts gunner Colburn and crew chief Andreotta were in full, horrified agreement that something was going wrong. As Thompson said in the 1989 British documentary Four Hours in My Lai, they "started seeing a lot of bodies—it didn't add up, you know, how many people were getting killed and wounded, and we weren't receiving any fire." Thompson radioed back to base there there was "a whole lot of unnecessary killing going on."

Thompson landed and confronted Lt. William Calley, who was busy eliminating civilians. Calley basically told Thompson to mind his own business. Meanwhile, Sgt. David Mitchell made sure nobody was still moving in the irrigation ditch chosen to be the grave of some 70 civilians. Stunned at the nonstop killing, which he later said reminded him of the Nazis, Thompson yelled: "You ain't heard the last of this!"

Some time later, the crew saw several Vietnamese being chased toward a bunker. That was the moment that Thompson chose a side, risking court martial or worse. He landed his helicopter between the soldiers and the civilians, and he told his men to shoot if the soldiers fired on Thompson or on the Vietnamese. They said they would.

Thompson successfully convinced the civilians to come out, and then he demanded help over the radio, convincing two nearby pilots to come to his aid. With aid from a nearby gunship more used to taking out Vietnamese than taking them out of harm's way, around a dozen civilians were removed from the wrath of Charlie Company. Not quite done, the three men took off to search for any more signs of movement.

Andreotta, with only a month left to live himself, saw something. He climbed into the slaughterhouse that had been an irrigation ditch and came out with a child. The crew hand-delivered them to a hospital, Thompson thinking of his own child at home all the while.

When Thompson returned to base he reported to Lt. Col. Frank Barker, who told the forces to stop the slaughter. Trent Angers, author of The Forgotten Hero of My Lai: The Hugh Thompson Story, says he has "no doubt that Hugh Thompson saved thousands of lives in Vietnam" by kicking up a fuss that halted Taskforce Barker, a plan to cleanse the entirety of the surrounding hamlets. Nobody was overtly saying "kill civilians," but like Medina that day they appeared ready to pacify the population however they could.

After a cover-up failed and the real story came out, the Army was prepared to prosecute the perpetrators. Thompson spent a year as the prosecution's best witness, all the while being browbeaten by powerful men. No less than President Richard Nixon appears to have urged his aide H.R. Haldeman to "discredit one witness" in the My Lai prosecution. Angers argues that Nixon went after Thompson personally.

It wasn't just Nixon. Congressmen, notably F. Edward Hébert (D-La.) and House Armed Service Chairman Mendel Rivers (D-S.C.) joined in the attack According to the chief My Lai prosecutor, Col. William Eckhardt, Hébert and Rivers wanted "to sabotage" the trials. A substantial majority of Americans opposed a life sentence for Lt. Calley, even many of those who agreed his actions were wrong. Calley became a twisted sort of folk hero while Thompson had his loyalty to his country questioned. Many of Thompson's fellow soldiers treated him like a leper.

On top of that, much evidence of the massacre was classified and could not be introduced in court. As a result, the first case—against Sgt. David Mitchell—was dismissed. Others collapsed. Everyone either said they were following orders or swore that they had ordered no such thing.

Eckhardt says he considers any accountability, even having a trial at all, a victory. Medina pled innocent (enough), other higher-ups were dead, still more were already out of the Army and its jurisdiction. Out of 14 people tried, only Calley was convicted, and he only got three years' house arrest—a pitiful punishment for at least 20 murders. "You know, you can blame Richard Nixon, you can do all sorts of things, but it was the country that demanded it," Eckhardt says.

Thompson ended up shutting up about the whole thing for 20 years, while still dutifully flying helicopters for the Army and counseling veterans. Neither he nor Colburn appear to have ever expressed regret or even doubt about their intervention, but it was a long time before they were rewarded for it. Nor were the perps given much punishment.

Thompson and Colburn got some justice eventually. But it wasn't the military or the public who demanded it. After seeing Four Hours in My Lai, a Clemson professor named David Egan was struck by the urge to find out if this soft-spoken Southern man shedding tears onscreen had ever been officially rewarded for putting humanity before country. Thompson had in fact been given and discarded a medal that flat-out lied about what happened at My Lai. Egan thought the man deserved a real one, and he spent the next several years bothering anyone important who would listen about Thompson.

Angers' book details much of the hand-wringing and foot-dragging that took place before Thompson was given the Soldier's Medal. When the medal was dangled in front of him, Thompson demanded that Colburn and Andreotta (posthumously) get one as well, and that the ceremony not be tucked away somewhere quiet. Eckhardt, Angers, and Colburn's widow Lisa all describe the 1998 ceremony at the Vietnam memorial as moving, and as a sort of release.

In the following years, Lawrence Colburn and Hugh Thompson returned to Vietnam several times and were bombarded with letters, praise, and media attention. Lisa Colburn tells Reason that her husband often mentioned the little boy Andreotta had taken from the ditch, wondering how he had fared. The boy, Do Ba, did not have an easy life, and the rest of his family all died at My Lai. But on a 1999 trip to Vietnam, a Quaker group reunited Colburn and Do Ba as a surprise. Lisa recalls that as they drove around on a bus, "Do Ba took Larry's hand, and he held onto [it] the entire day…he wouldn't let go, he held his hand the entire time."

The effects of the men's actions radiated further. Both men were honored to be asked to lecture on military ethics later in life. Says Eckhardt: "You know what the military teaches about My Lai right now?…It says basically, follow Thompson."

Calley and Medina are still alive; the three men who resisted their violent fever are not. But 50 years on, remember these exceptional human beings who did the right thing when they were outnumbered, even if no people in this story got what they deserve. "Most stories, from Greek mythology on, have a hero and a villain," says Eckhardt. "And we know which one's which in this story. And I think we need to concentrate on the hero."