Appointed to the U.S. Military Academy at West Point where he graduated in 1952.
Assigned to the 22nd Fighter Day Squadron at Bitburg Air Base, Germany where he spent three and a half years flying the F-86 and F-100 fighter aircraft.
Attended the Air Force Test Pilot Program at Edwards Air Force Base for advanced aviation training. He was then transferred to Wright-Patterson Air Force Base as a weightlessness and extended flight training captain.
Was one of nine astronauts selected by NASA for Project Gemini.
Served as Pilot for the Gemini 4 flight, a four-day mission from June 3 to 7, 1965. During this flight, he was the first American to make a spacewalk.
Selected as Senior Pilot for the first Apollo mission on March 21, 1966.