Boyd flew 22 combat missions in F-86 Sabres during the Korean War. Though he saw limited actual air-to-air combat (arriving near the end of the war), the experience gave him firsthand exposure to the realities of aerial warfare and planted the seeds of his lifelong obsession with understanding why some pilots consistently won and others lost. He observed that American pilots achieved a 10:1 kill ratio over MiG-15s despite the MiG's superior performance specifications — a puzzle that would eventually lead to E-M theory.