World War I fundamentally altered Europeans' views concerning warfare. New lethal technologies, combined with unprecedented casualties and the horrors of trench warfare, purged warfare of any romantic notions. The Great War also caused people to question Enlightenment values of progress, rationality, and human perfectibility. Modern philosophy and art sprang from this postwar disillusionment.
Also I have found some short videos about totalitarian leaders of the inter-war period. They are definitely worth 5 minutes of your time and are posted in the order they rose to power. Note Mussolini's ability to change political ideologies, much like Otto von Bismarck. Also, Hitler's failures at Munich forced him to adopt a more political rise to power similar to Stalin.