On a visit to the former battlefield of Khe Sanh, scene of one of the bloodiest standoffs of the Vietnam War, the only people Chuck Searcy encountered on the broad, barren field were two young boys who led him to an unexploded rocket lying by a ditch.

One of the youngsters reached out to give the bomb a kick until Mr. Searcy cried out, “No, Stop!”

“It was my first encounter with unexploded ordnance,” Mr. Searcy said of that moment in 1992. “I had no idea that I would be dedicating my life to removing them.”

It was not Mr. Searcy’s first encounter with Vietnam. He served there as a soldier in 1968, the same year as the battle of Khe Sanh, and came away disillusioned.

As a U.S. Army intelligence analyst, he had had access to a full range of raw information, from the enemy’s body counts to exaggerated claims of American progress.

“We got to see almost everything,” he said in a recent interview. “And I saw that our friends back home were being given information that was not just misleading but deliberate lies.”

“That shocked us as innocent young men,” he added, “and we began to feel that the system was broken.