As US military involvement in South Vietnam escalated rapidly in 1963, the US Air Force braced itself for imminent conflict. The seasoned pilots were well aware that air-to-air battles would be difficult when pitched against formidable aircraft such as the Soviet Mig 21s and Mig 25s.Long gone were the days of dogfighting; the future belonged to long-range encounters using air-to-air missiles.As part of this new doctrine, the Air Force sought to develop a new aircraft that followed the Energy-Maneuverability formula that predicted an aircraft’s performance based on weight and capabilities.As the war in Vietnam raged on and the urge for a new fighter increased, Northrop rose to the occasion and introduced an aircraft that embodied these ideals: the YF-17 Cobra.—