Sergeant Harper was a member of Battery D, 82nd Anti-Aircraft Artillery (Automatic Weapons) Battalion, 2nd Infantry Division. He was taken Prisoner of War while fighting the enemy near Hoensong, South Korea on 13 February 1951 and died while a prisoner on 6 August 1951. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Harper was awarded 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.