Most relatives long ago gave up hope of learning what became of them or of recovering their remains.
But CBS News Correspondent Richard Schlesinger reports on how modern science and plain old luck helped recover one of America's forgotten heroes.
It would be hard to find any place as remote as a mountaintop, 6,000 feet above Guangxi province in Southern China. But a particular spot there has become near and dear to one family in Florida looking for one of their own lost in World War II.
All his life Grady Kearsey has been hearing stories about his uncle Robert, who died before he was born and who kept fighting the war even after one brother had been killed.
"He decided that he wanted to get even somehow. And he wanted to get back into the fight. (Of) course, that's when he volunteered to go back to Southeast Asia and fight...the Japanese," Grady Kearsey says.
Sergeant Robert Kearsey was aboard an American bomber returning from a raid on a Japanese port when it crashed in the mountains of China.
For more than 50 years the wreckage lay undiscovered until two farmers found it in 1996. The U.S. Army then began trying to recover the wreckage and the remains of the crew, including those of Robert Kearsey.
"My first thought was this is going to be extremely difficult. And my first concern was, will we even be able to recover these men?" says Johnnie Webb, who runs the army's Central Identification Lab at Hickham Air Force Base near Pearl Harbor. It took Webb's people three years to clear this mountainside.
"We didn't want to leave anybody on that mountain," he says.
"The discovery of this aircraft was a huge lift for our family," says Grady Kearsey.
Recovering the remains was tough enough. Identifying them was even tougher. And being able to tell which were Kearsey's was tougher still.
Until recently it was almost impossible to reliably identify bone fragments. That was before new ways of using DNA were discovered.
The new DNA technology could have an enormous effect on the work being done at Hickham because it makes it easier to identify older remains. And there are still more than 78,000 missing servicemen and women from World War II.
The problem was, in order to use the new science, the Army lab needed a DNA sample from a maternal relative of Robert Kearsey, and the Kearseys thought that side of their family had died out.
"We were having a very difficult time procuring a DNA sample," Grady Kearsey says.
But the army had a secret weapon, a big surprise for everyone, especially the Kearsey family.
Read the second part of this report in Genealogy To Rescue.