Sergeant First Class Gruebbeling was a veteran of World War II. In Korea, he was a member of Company I, 3rd Battalion, 31st Infantry Regiment, 7th Infantry Division. He was listed as Missing in Action while fighting the enemy near the Chosin Reservoir in North Korea on December 3, 1950. He was presumed dead on December 31, 1953. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.