Two causes of World War II were the harsh provisions of the Treaty of Versailles that ended World War I and the rise of nationalist leader Adolf Hitler.
Treaty of Versailles The new German government was required to surrender approximately 10 percent of its prewar territory in Europe and all of its overseas possessions. The harbor city of Danzig (now Gdansk) and the coal-rich Saarland were placed under the administration of the League of Nations, and France was allowed to exploit the economic resources of the Saarland until 1935. The German Army and Navy were limited in size. Kaiser Wilhelm II and a number of other high-ranking German officials were to be tried as war criminals. Under the terms of Article 231 of the treaty, the Germans accepted responsibility for the war and, as such, were liable to pay financial reparations to the Allies, though the actual amount would be determined by an Inter-Allied Commission that would present its findings in. Germans would grow to resent these harsh conditions imposed by the Treaty of Versailles.
Adolf Hitler a charismatic leader who rose to power in Germany during intra-war period. German supported him because they needed a strong leader. He promised higher prices for farmers, jobs for unemployed workers, profits for small businesses and an end to the communist threat for large industrialists. After a year in office, Hitler began a compaign to revise the Versailles Treaty. He declared himself the Third Reich. He withdrew Germany from the League of Nations, renounced the Versailles Treaty and re-armed Germany. Hitler annexed Austria and threatened Poland. Germany invaded Poland and World War II began. The American public was decidedly isolationist and antiwar. When France fell to the Nazis in May 1940, Britain stood alone. Roosevelt began a remarkable and voluminous secret.