Captain Appenfelder was a member of Headquarters and Service Company, 2nd Engineer Combat Battalion, 2nd Infantry Division. He was taken Prisoner of War while fighting the enemy near Kunu-ri, North Korea on 30 November 1950 and died while a prisoner on 16 January 1951. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

For his leadership and valor, Captain Appenfelder was awarded the Bronze Star Medal, the Purple Heart, 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.