A Schnellbomber (German; literally "fast bomber") is a bomber that relies upon speed to avoid enemy fighters, rather than relying on defensive armament and armor. Concept The concept developed in the 1930s when it was believed that a very fast bomber could simply outrun its enemies. Omitting defensive armament allowed for significant reduction in drag (there would be no turrets, gondolas or gun barrels protruding from the fuselage) as well as weight (no guns, ammunition or manning crew members would be required on board), resulting in improved performance. Adolf Hitler was a staunch supporter of the Schnellbomber and directed the Luftwaffe to only develop medium bombers, while the USA and British developed both twin-engine medium bombers and four-engine heavy bombers. Twin-engine medium bombers, while best adapted as the Schnellbomber, lacked the payload and range of heavy bombers which put them at considerable disadvantage for strategic bombing. In strategic bombing raids the Luftwaffe made do with medium bombers with limited fighter escort from the Messerschmitt Bf 109 and its heavier twin-engine Bf 110 counterpart due to the lack of a truly long-range fighter. The Allies by contrast used slow but heavily armed bombers such as the B-17 Flying Fortress deployed in combat box formation, with the long-range North American P-51 Mustang initially in escort and later in forward role conducting a "fighter sweep" in order to intercept attacking German fighters. Development The first aircraft adopted for the Schnellbomber role was the single-engine Heinkel He 70, but it soon was replaced by the twin-engine Dornier Do 17 in that role. In the 1937 air races in Switzerland the Do 17 won a number of speed records, apparently demonstrating the value of the concept. However, experience of the Spanish Civil War demonstrated that the Do 17's speed when loaded with military equipment was insufficient to escape interception, and armament had to be added to give it some defensive fighting capability. Bomber development temporarily outpaced fighter development in the 1930s. The last generation of biplane fighters (like the Gloster Gladiator and Polikarpov I-15) that had been placed in service during that decade could not catch the privately created Bristol Type 142 twin-engined light bomber prototype in 1935. However by the end of the 1930s, low-wing monoplane fighters like the Hawker Hurricane and the Supermarine Spitfire had entered service, and they had the performance to catch up with the Schnellbomber, and dramatically outgun it by