Boyd's key concept was that of the decision cycle or OODA loop, the process by which an entity (either an individual or an organization) reacts to an event. According to this idea, the key to victory is to be able to create situations wherein one can make appropriate decisions more quickly than one's opponent. The construct was originally a theory of achieving success in air-to-air combat, developed out of Boyd's Energy-Maneuverability theory and his observations on air combat between MiG-15s and North American F-86 Sabres in Korea. Harry Hillaker (chief designer of the F-16) said of the OODA theory, "Time is the dominant parameter. The pilot who goes through the OODA cycle in the shortest time prevails because his opponent is caught responding to situations that have already changed."