Sergeant First Class Slagle was a member of Company C, 1st Battalion, 32nd Infantry Regiment, 7th Infantry Division. He was listed as Missing in Action while fighting the enemy in North Korea on 26 April 1951. He was presumed dead on 31 December 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

For his leadership and valor, Sergeant First Class Slagle was awarded the Bronze Star Medal, the Purple Heart, the Combat Infantryman 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.