Flying low over the village of My Lai in South Vietnam, helicopter pilot Hugh Thompson frantically scanned the ground below. The enemy must be there, he thought. Must be. What else could explain what he had just seen?

But the "enemy" Thompson would confront that day almost exactly 30 years ago wore U.S. uniforms. His battle with them haunts him still.The My Lai massacre, which left some 500 Vietnamese civilians dead and led to the court-martial of Lt. William Calley, stands as one of the darkest moments in American military history.

There is a sliver of light: Thompson's little-known story.

It's the story of a man who obeyed his convictions, who defied superiors, who placed his body between villagers and his fellow soldiers, who ordered his gunner to fire on American troops if necessary. It's also a story of long-withheld recognition of this bitter brand of heroism, which some blame on a nation's shame.

On Friday, the story gets an overdue concluding chapter.

By the glossy granite walls of the Vietnam Veterans Memorial in Washington, Thompson is to receive the pres-tigious Soldier's Medal for his action in saving some villagers and stopping American troops from killing more on March 16, 1968.

Some insist the military was reluctant to publicly honor what Thompson did. Shortly after My Lai, he received the Distinguished Flying Cross as his crew mates received Bronze stars, but he looks on that cynically.

"It was only to keep me quiet," he says.My Lai was deceptively quiet that March day.

Thompson, then 24, and his two-man crew were to swoop down over the village and draw fire so helicopters behind them could destroy the enemy with machine gun and rocket fire.

They never drew fire.

But they spotted a young Vietnamese girl, injured and lying on the road. Thompson marked the spot with a smoke grenade, radioed for help and then hovered nearby.

He and his crew watched in horror as an American Army officer walked up to the girl, flipped her over with his foot - and shot her dead.

They saw the bodies of Vietnamese children, women and old men piled in an irrigation ditch. Thompson landed and implored American soldiers: "Help the wounded."

Instead, troops fired into the bodies.

Thompson wracked his brain for an explanation.

"We wanted to find something that would point the blame to the enemy, but it just didn't work," the gruff, graying Thompson says. "It all added up to something we just didn't want to believe."

He was moved to action when he spotted villagers crowded in a hut - an old woman standing in the doorway, a baby in her arms, a child clutching her leg.

American soldiers were approaching.

"These people were looking at me for help, and there was no way I could turn my back on them," Thompson recalls.

He told the officer in charge to help him get the villagers out. The officer replied that the only help the villagers would get was a hand grenade, Thompson says.

So he placed his chopper down in front of the advancing Americans and gave his gunner, Lawrence Colburn, a simple, direct order: Train your M-60 on the GIs.

Thompson radioed to two gun ships behind him, and together they airlifted a dozen villagers to safety.

He flew back to the irrigation ditch where his other crew mate, Glenn Andreotta, saw something move. Andreotta jumped out and waded through the bodies until he reached a 2-year-old boy, still clinging to his dead mother. He handed him to Colburn.

"You've never seen shock like this," Colburn says of the child.

The standoff lasted 15 minutes.

Retelling it, Thompson shields his teary eyes at one point. "I had a son at home about the same age," he finally says.

Few Americans ever knew of Thompson's deed until David Egan, a professor emeritus at Clemson University, saw a BBC documentary on My Lai 10 years ago in which Thompson was interviewed.