World War II began in Europe in 1939 and spread to the US by 1941, profoundly changing both nations and the world. The war ended the Great Depression as resources were mobilized for the war effort. Both Hitler and Roosevelt rose to power during the economic crisis of the 1930s but lacked coherent economic plans, instead appealing to nationalist sentiments. Their rise coincided with the failure of international cooperation through bodies like the League of Nations to prevent aggression by fascist regimes in Germany and Italy.