Sergeant First Class Rule was a member of Company A, 1st Battalion, 8th Cavalry Regiment, 1st Cavalry Division. He was seriously wounded while fighting the enemy in South Korea on October 9, 1950 and returned to duty on October 25, 1950. He was listed as Missing in Action while fighting the enemy near Unsan, North Korea on November 2, 1950. He was presumed dead on December 31, 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.