The hang glider lost some importance from the introduction of wing warping in 1902 by the Wright brothers and subsequently of aileron control by the French. When World War 1 ended in 1918, the Treaty of Versailles practically ended engine-driven flights in Germany, thus, in the 1920s and 1930s, while aviators and aircraft makers in the rest of the world were working to improve the performance of powered aircraft, the Germans were designing, developing and flying ever more efficient gliders and discovering ways of using the natural air flows in the atmosphere to make them fly farther and faster. These activities on Wasserkuppe promoted a renaissance of gliding aviation. Many of these gliders flown in 1920 were hang gliders in that they were controlled by the pilot's weight shift alone. The first Wasserkuppe glider competition was held in 1920, and from 1924 they were organised by Rhön-Rossitten Gesellschaft. Over the next decade, the contest grew in popularity. As many as 70 glider clubs from Europe sent their best gliders and pilots to compete for duration, altitude and distance prizes, the most coveted prize was that donated by President Paul von Hindenburg. As many as 60,000 spectators dotted the mountain slopes to watch these events. Virtually every European aeronautical engineer of the time tested and modified their aircraft there and reports were generated. Some competing hang glider designers were Alfried Gymnich, Gottlob Espenlaub, Alexander Lippisch, Heinz Schneider, Francis Chardon, Willi Pelzner, and Hans Richter while engineer Henri Mignet was busy in France and Czesław Tański was busy in Poland.