The Defense Department says Army Sgt. 1st Class Gunther Wald was part of a Special Forces reconnaissance patrol operating near the Vietnam-Laos border in 1969.
The Pentagon says Wald and two other Americans were wounded during an ambush. There was no sign of the men when a search-and-rescue team, hampered by the enemy and weather, reached the site eight days later.
A Vietnamese citizen led investigators to human remains he had discovered in 2007. They were excavated in 2010 and later identified.
Wald and the others will be buried in a single casket at Arlington National Cemetery on Thursday.