The rise of Nazism and fascism included a revival of the nationalist spirit and a rejection of many post-war changes. Similarly, the popularity of the Stab-in-the-back legend(German: Dolchstoßlegende) was a testament to the psychological state of defeated Germany and was a rejection of responsibility for the conflict. This conspiracy theory of betrayal became common, and the German populace came to see themselves as victims. The Dolchstoßlegende's popular acceptance in Germany played a significant role in the rise of Nazism. A sense of disillusionment and cynicism became pronounced, with nihilism growing. Many believed the war heralded the end of the world as they had known it because of the high fatalities among a generation of men, the dissolution of governments and empires, and the collapse of capitalism and imperialism.
Communist and socialist movements around the world drew strength from this theory and enjoyed a new level of popularity. These feelings were most pronounced in areas directly or harshly affected by the war. Out of German discontent with the still controversial Treaty of Versailles, Adolf Hitler was able to gain popularity and power. World War II was in part a continuation of the power struggle never fully resolved by the First World War; in fact, it was common for Germans in the 1930s and 1940s to justify acts of international aggression because of perceived injustices imposed by the victors of the First World War.
The establishment of the modern state of Israel and the roots of the continuing Israeli-Palestinian Conflict are partially found in the unstable power dynamics of the Middle East which resulted from World War I. Prior to the end of the war, the Ottoman Empire had maintained a modest level of peace and stability throughout the Middle East. With the fall of Ottoman government, power vacuums developed and conflicting claims to land and nationhood began to emerge. The political boundaries drawn by the victors of the First World War were quickly imposed, sometimes after only cursory consultation with the local population. In many cases, these continue to be problematic in the 21st-century struggles for national identity. While the dissolution of the Ottoman Empire at the end of World War I was pivotal in contributing to the modern political situation of the Middle East, including the Arab-Israeli conflict, the end of Ottoman rule also spawned lesser known disputes over water and other natural resources.