For Americans fighting in Vietnam, determining who was the enemy was a huge problem, and one that was not readily resolved. Since the war was essentially a civil war between the Communist-led Viet Cong and North Vietnamese and the American-supported South Vietnamese, it was almost impossible to know who supported the Communists and who did not. During the day, Vietnamese villagers were frequently peaceful and friendly toward American soldiers and often worked as merchants, maids, or barbers for them in their base camps. But at night, these same villagers became the enemy who slipped through fences to blow up the military compounds. Many Americans have reported their dismay at discovering that their favorite maid or shoeshine boy was shot trying to infiltrate the base's perimeter during an attack by the VC at night.

The Americans were also unsure about the Vietnamese because many children were...