Initially, President Roosevelt declared neutrality while Prime Minister Churchill watched without action as WWII began. After France fell, Roosevelt and Churchill formed an alliance to save Britain. Political manipulation on both sides led to a complicated wartime effort. The war ended the Great Depression worldwide and reinvented the US as the global police. It also devastated Western Europe's empires, started the Cold War, and made Japan a superpower, though Japanese attacks on Pearl Harbor caused widespread American hatred against Japan.