Gen Gregory completed over 35 years of Air Force service before retiring in 1988. He held every level of command in the fighter business including a fighter squadron in the Southeast Asia war; a fighter wing at Moody AFB, Georgia; an Air Division at George AFB, California; the Tactical Weapons Center at Nellis AFB, Nevada (included the largest fighter wing in the Air Force, the Fighter Weapons School, the Aggressors, Red Flag exercises, and fighter testing and development); Twelfth Air Force at Bergstrom AFB, Texas (responsible for 13 fighter wings, 1,100 aircraft and 50,000 active duty Air Force people plus an additional 550 aircraft and 25,000 people in Guard and Reserve units); Seventh Air Force at Osan AB, Korea; Commander of U.S. Air Forces, Korea; Deputy Commander for all U.S. Forces in Korea; and Deputy Commander of the United Nations Command, Korea (in this capacity he was senior U.S. representative to the committee for the Status of Forces Agreement). His last assignment was as Commander in Chief of the Pacific Air Forces where he was responsible for 60,000 Air Force people throughout the Pacific theater.

General Gregory was a fighter pilot throughout his career flying 40 different aircraft including German, British, Russian and Korean aircraft while recording nearly 7,500 flying hours and 250 combat missions. As the Air Warfare Center Commander in 1981-83, he was charged with bringing the stealth fighter to operational status in Tactical Air Command. During this same period he headed the conversion of the USAF Thunderbirds to F-16s from T-38s.

His military decorations include the Defense Distinguished Service Medal, Distinguished Service Medal, Legion of Merit with one Oak Leaf Cluster, Distinguished Flying Cross with two Oak Leaf Clusters, Bronze Star Medal, Meritorious Service Medal with one Oak Leaf Cluster, and the Air Medal with 13 Oak Leaf Clusters.

Since retiring, he has remained active in matters regarding national and international security. He continues as a senior advisor to the Commanders in Chief of U.S. Forces, Korea regarding the air defense of the Republic of Korea. General Gregory is a senior partner in Kistler Aerospace Corporation, a privately funded company which is designing, building and will commercially operate a fleet of fully reusable aerospace vehicles that will be capable of placing communications satellites into low earth orbits at substantially reduced prices when compared to existing expendable launch vehicles. Gen Gregory was born and raised in Somerset, Kentucky and is a graduate of the University of Kentucky. In 1985 he was inducted into the UK Hall of Distinguished Alumni.