General Capp retired from the military in 1983 after almost 36 years of service in the Illinois National Guard, the U.S. Army and the U.S. Army Reserve. During his military career he was highly decorated, earning the Distinguished Service Medal; the Meritorious Service Medal; the Army Commendation Medal; the Army Reserve Components Achievement Medal with Oak Leaf Clusters; the United Nations Service Medal; the Armed Forces Reserve Medal with two hourglass devices (denoting 20+ years of service); the National Defense Service Medal; the Army Service Ribbon; and the Bronze Order of the de Fleury Medal, presented to an outstanding individual who has rendered significant service or support to an element of the Engineer Regiment.