Corporal Harmon was a medic with the Medical Company, 29th Infantry Regimental Combat Team. He was taken Prisoner of War while tending his wounded comrades near Hadong, South Korea on 27 July 1950 and was killed by a guard on 30 September 1950. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Harmon was awarded the Purple Heart, the Combat Medical Badge, the Prisoner of War Medal, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.