AMERICAN NOTES: The Known Soldiers

Construction is to begin in Arlington National Cemetery this autumn on the fourth Tomb of the Unknown Soldier — to be dedicated to the U.S. fighting men who have fallen in Viet Nam.

There is a macabre hitch in the Army memorial agency's plans, though. Of the 45,810 Americans killed in Viet Nam between Jan. 1, 1961 and July 8, 1972, all have been identified.

Two factors have created this peculiar problem. Viet Nam is a small-unit war, where most of the fighting has involved companies in paddyfields and hamlets. In World War II,...