Staff Sergeant Callaghan was a member of Company A, 1st Battalion, 7th Marines, 1st Marine Division. He was seriously wounded while fighting the enemy in Korea and died of those wounds on 26 October 1952.

Callaghan was awarded the Purple Heart, the Combat Action Ribbon, 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.