 Soon more difficult climbs were made, which originally were graded level 0 and 00.In 1923, the German mountaineer Willo Welzenbach compressed the scale and turned the order around, so that level 00 became level IV–V.This "Welzenbach scale" was adopted in 1935 by French mountaineers like Lucien Devies, Pierre Allain and Armand Charlet for routes in the Western Alps and finally in 1947 in Chamonix by the Union Internationale des Associations d'Alpinisme.