WASHINGTON — It's the rarest and most prestigious military honor, made rarer still by a 42-year delay attributed to lost paperwork.

But Wednesday, Army Spec. Leslie H. Sabo Jr. finally was recognized for an act of wartime heroism that took his life at age 22 as he saved comrades when his platoon was ambushed in Cambodia during the Vietnam War.

"Along with Les, seven other soldiers gave their lives that day," President Obama said as he presented the Medal of Honor to Sabo's widow, Rose Mary Sabo-Brown. "And those who came home took on one last mission — and that was to make sure America would honor their fallen brothers. They had no idea how hard it would be or how long it would take."

Bravo Company comrade George Koziol, who has since died of cancer, nominated Sabo of Ellwood City for a Medal of Honor not long after that harrowing day, but the paperwork was lost until 1999. That's when another veteran, Alton "Tony" Mabb, came across it while doing research in the National Archives in College Park, Md. He was looking for story ideas for his column in Screaming Eagle magazine, the official publication of the 171st Airborne Division, and asked to see records of Medal of Honor recipients.

"They came out with this box and there was quite a bit of material — 50 or 100 pages — on Leslie Sabo," including witnesses' accounts of the May 1970 ambush that killed eight and wounded 28, Mabb recalled. Next, he checked Sabo's military records to see if the medal ever was awarded, but the highest honor listed was a bronze star.

That's when he took on Sabo's case as a personal project, even though he had never met the man or even heard his name before.

Mabb, 62, told his story in a telephone interview from his home in Jacksonville, Fla., where he works for the Internal Revenue Service as a tax-law expert.

"I've had some uncomfortable conversations over the years [with members of Sabo's company]. People were reliving their stuff, and it's hard," said Mabb, who served in Vietnam in 1970 and '71.

Their stories weave together a harrowing tale of a badly wounded soldier crawling toward enemy lines to hurl grenades at his North Vietnamese attackers and then stepping back into the line of fire to help provide safe passage for fellow wounded Americans who were being airlifted out.

Without their willingness to retell their stories, and without Mabb's efforts to find them, Sabo's family never would have known of his heroism.

Finding out "was all pretty shocking. When Leslie got killed, all they had told me was that he was killed by enemy fire, and that was all I knew," Sabo-Brown said.

Obama described the attack this way: "Some 50 American soldiers were nearly surrounded by some 100 North Vietnamese fighters. … Les was in the rear — and he could have stayed there. But those fighters were unloading on his brothers, so Les charged forward and took several of those fighters out.

"An enemy grenade landed near a wounded American. Les picked it up and threw it back. And as that grenade exploded, he shielded that soldier with his own body," he continued.

"The enemy zeroed in with everything they had. But Les kept crawling, kept pulling himself along, closer to bunker, even as the bullets hit the ground all around him.

"And then, he grabbed a grenade and pulled the pin. It's said he held that grenade and didn't throw it until the last possible moment, knowing it would take his own life, but knowing he could silence that bunker. He saved his comrades, who meant more to him than life."

The Medal of Honor is awarded to members of the military who conspicuously demonstrate extraordinary gallantry while engaged in military action. Of the 2.1 million men who served in Vietnam, only 246 received it — 154 of them posthumously.

Since 1863, when the medal was made a permanent decoration, 3,468 have been awarded.