During its initial stages in the end of the 19th and the beginning of the 20th century, Slovenian alpinism was several decades behind the British and the Alpine countries, welldeveloped in the field of mountain climbing. It was under a lot of pressure, especially from the German mountaineers who wanted to climb the most important lines and climbing routes to the summits in the Slovenian mountains. In the following article the author focuses on the development of the Slovenian mountaineering and especially alpinism, as well as on its progress in the interwar period when the difference between the Slovenian climbers and the best alpinists had already diminished significantly. By analysing the existing archive sources and literature, the author attempts to determine the number of mountaineers killed during World War II and the consequences for the development of the Slovenian alpinism.