Sergeant Charles Robert Jenkins arrived at South Korea's Camp Clinch in 1964. Although he had already served in the Army for six years and had overseas postings, this was by far his most perilous assignment. The Americans patrolled along the Demilitarized Zone (DMZ) that separated the two Koreas and occasionally drew hostile fire from North Korean soldiers across the border--even though an official cease-fire had been in place since 1953. Jenkins had served with enough distinction to find himself leading reconnaissance missions. But he couldn't cope with the danger.
A seventh-grade dropout from Rich Square, N.C., Jenkins possessed an intelligence that...