Assisted by his top aide Harry Hopkins and with very strong national support, he worked closely with British prime minister Winston Churchill, Soviet general secretary Joseph Stalin, and Chinese Generalissimo Chiang Kai-shek in leading the Allied Powers against the Axis Powers. Roosevelt supervised the mobilization of the U.S. economy to support the war effort and implemented a Europe first strategy, initiating the Lend-Lease program and making the defeat of Germany first a priority over that of Japan. His administration co-ordinated massive wartime efforts such as the construction of the Pentagon and the Manhattan Project, which saw the creation of the atomic bomb. His foreign policy mirrored Wilsonian ideals which prompted Roosevelt to make his highest postwar priority being the establishment of the United Nations. Roosevelt expected the United Nations to replace the now defunct League of Nations and to be led by Washington, Moscow, London, and Nanjing.[a] These states collectively called the Big Four would work to resolve all major world problems. It was under his wartime leadership that the United States became a superpower on the world stage.[6]
Roosevelt won re-election in the 1944 presidential election on his post-war recovery platform. 