In many ways, World War I and its aftermath helped to create the political, social, and economic conditions for the rise of European dictatorships.

In Germany, for example, the harsh demands of the Treaty of Versailles greatly inflamed nationalist sentiment. The Treaty laid the sole blame for the War at Germany's door, which the vast majority of Germans felt was completely unfair. The Treaty also imposed crippling reparations payments on Germany that generated considerable economic hardship.

This toxic combination of national humiliation and economic hardship created the ideal breeding ground for extremist politics, of both the right and the left. The far-right National Socialist German Workers' Party (NSDAP), or Nazis for short, were particularly adept at exploiting grievances arising from the Versailles Treaty to their own advantage.

Under the leadership of Adolf Hitler, the Nazis promised that, if they came to power, they would make Germany great again, building a strong economy and a powerful army befitting a great power. At first, the Nazis' message went largely unheeded, but as Germany sank deeper into economic chaos, more people started to throw in their lot with Hitler's party.

Ordinarily, most people would not have paid much attention to a fringe party of the extreme right, but these were no ordinary times. As the German economy became mired in hyperinflation and mass unemployment, a growing number of Germans looked to the Nazis for a solution to their problems.

Coupled with the disastrous state of the German economy, the abiding sense of national shame and humiliation arising from the imposition of the Versailles Treaty meant that Germans were all too ready to believe the Nazis' promises that they, and only they, were capable of restoring national greatness.

World War I most notoriously led to the rise of a Nazi dictatorship in Germany in the 1930s. Reasons for this included the humiliating Treaty of Versailles that the Germans were forced to sign which forced them to assume full blame for the war. Other factors in the treaty that led to the rise of Hitler included a clause limiting the German army to 100,000. The army had been an important and highly respectable employer of poor but ambitious young men before the war.

With that avenue cut off, many disaffected youths joined right wing militias, such as the Nazi brown shirts, bent on overthrowing what they considered the illegitimate and "Jewish" Weimar Republic. Another factor leading to rise of Hitler was the traumatic impact of World War I on English and French populations, making their governments shrink from anything that looked like another armed conflict. They could have toppled Hitler early but were afraid to do so.

World War I also led to the rise of the dictatorial Soviet communist regime in Russia. This war, which the incompetent czar Nicholas II decided to run himself, was horribly mismanaged, a situation the communists exploited. Very high war deaths and widespread civilian hunger led to strikes and finally uprisings that deposed the czar and led to Lenin and Stalin's rise.

In Italy, the Italian fascists were able to topple the weak, unstable government of King Victor Emmanuel III in 1921 to seize dictatorial power for their leader, Mussolini.

The aftermath of World War I paved the way for the rise of dictators in Europe. The Treaty of Versailles that concluded World War I placed heavy reparations, or payments, on Germany that the country could not finance. The post-war years were marked by instability as well as humiliation in Germany, as Germany also had to accept blame for causing World War I. In addition, Germany lost land in the Treaty of Versailles, and the German people, charged with a sense of nationalism, looked for a leader who could restore their economic power and reclaim their place in the world. In 1933, they found this leader in Hitler.

Italy had entered World War I on the side of the Allies and was promised a great deal of land in return, including parts of the Ottoman Empire, islands in the Adriatic, and lands along the border of Austria-Hungary. The Allies did not deliver on these promises, making the Treaty of Versailles unpopular in Italy. As a result of these broken promises, the country harbored sentiment against England and France, helping Mussolini's rise, as he built on this sentiment to gain power.

The Treaty of Versailles also resulted in a weak League of Nations, an international peacemaking body. The United States never signed the covenant, making the League of Nations relatively weak and unable to prevent future wars. 

The three most important dictators to arise in Europe in the decade or so after the First World War were Benito Mussolini in Italy, Joseph Stalin in the Soviet Union and Adolf Hitler in Germany.  These men rose to power essentially because their countries had in some way been made unhappy by the outcome of that war.

Mussolini came to power first.  His rise was connected in part to the war.  In the Treaty of Versailles, the Italians had not gotten what they had been promised when they entered the war.  This upset them greatly and led to nationalist sentiment.  The war also helped to disrupt the economy and society, opening the way for conflict that led to the rise of the fascists.

Hitler’s rise was much more clearly connected to WWI.  The Treaty of Versailles had punished Germany harshly.  Hitler’s rise was predicated on rousing German anger at this treatment and at the alleged “stab in the back” that caused Germany to lose WWI.  His Nazi ideology was able to capitalize on those emotions.

Stalin’s rise was also connected to WWI.  The ineptitude of the Russian war effort had helped to overthrow the old regime.  The Bolsheviks were able to take power in part because the war had discredited the monarchy.

WWI contributed to the rise of dictatorship, then, because it caused some countries to be unhappy with the world order that came out of the war.