Private First Class Armstrong was a medic with the Medical Company, 34th Infantry Regiment, 24th Infantry Division. He was Killed in Action while tending his wounded comrades near Taejon, South Korea, on 20 July 1950.

Armstrong was awarded the Purple Heart, the Combat Medical Badge, 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.