Private First Class Calkins was a member of Company A, 1st Battalion, 27th Infantry Regiment, 25th Infantry Division. He was listed as Missing in Action while fighting the enemy in South Korea on 24 July 1950. He was presumed dead on 31 December 1953. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Calkins was awarded 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.