In May 1969, Chuck Vander Luitgaren was one of hundreds of American soldiers who fought in the Battle of Hamburger Hill, one of the major engagements of the Vietnam War. This week, after half a century, he and 11 fellow veterans returned to the site of the battle, near Vietnam’s border with Laos. Hobbled by age and haunted by memories, they climbed approximately 3,000 feet up the hillside, accompanied by their successors in the Army’s storied 101st Airborne Division.

Thunder and cold rain triggered a flashback as Mr. Vander...