Political and economic conditions following WWI led to rise of fascism in Europe. The Great Depression caused widespread unemployment and hyperinflation in Germany, punished severely by the Treaty of Versailles. Fascist dictators like Hitler and Mussolini rose to power. As conflict grew in Europe and Asia, American policy evolved from neutrality to involvement. Japan's aggression in Asia increased tensions with the U.S. The U.S. imposed sanctions on Japan. On December 7, 1941, Japan attacked Pearl Harbor, bringing the U.S. into WWII fighting on two fronts in both Europe and the Pacific.