 After high school, Hagan enlisted in the United States Navy in December 1964 and attended basic training at Recruit Training Center, San Diego, California.He then attended Electronics Technician "A" School at Naval Training Center, Treasure Island, California, and completed a short assignment at Naval Air Test Center Patuxent River, Maryland.After he completed Ground Control Approach Radar Technician School at Naval Air Technical Training Center, Glynco, Georgia, Hagan reported to Naval Air Station, Whidbey Island, Washington,ultimately becomin as the Leading Petty Officer for the Air Search Radar Maintenance Division.