The growth in size, lethality, and technology of the German Luftwaffe was of concern to some defense planners in the United States before American entry into the war. Learning about the Luftwaffe became a significant effort once the conflict broke out in Europe. From defectors with German aircraft to battlefield trophies and combat crew reports, the race to understand German aero technology took on sometimes heroic proportions. After the war, German technology infused American aerospace developments in many ways: German ribbon parachutes were evaluated for high-speed bailouts; sweptwing leading edge slat technology benefited the F-86 Sabre; overall comprehension of sweptwing benefits to fast jet aircraft was validated; pulse jet V1s and supersonic V2 rockets boosted American drone weapon, ballistic missile, and space exploration efforts. In this volume, Frederick A. Johnsen traces that path of discovery.