Hitler did declare war on the U.S. with almost no thought and no advanced planning. Hell, the German war economy wasn't even fully moblilized until 1942 - anybody with a brain would've have known that Germany could not compete with the United State's manufacturing capabilities and industrial output. It was a mistake that guarenteed Germany's defeat. What I don't understand, is why Hitler felt loyalty to Japan and declared war on the US to back them up, when Japan wasn't loyal enough to invade the Soviet Union from the eastern side and help Germany out! Weren't Stalin's Siberian divisions, which played such a vital role in blunting operation Typhoon, transfered to the Moscow area to fight the Germans after it was clear that the Japanese weren't a threat to Russia's eastern flank? What was the point on an alliance with Japan, then? Some help that ally was - they expediated the United States entry into the war by bombing Pearl Harbor! We all know Chruchill was putting a lot of presure on Roosevelt to help him fight the Germans, but the American people saw Japan on their only immediate enemy. Hitler declaring war on the U.S. gave Roosevelt the perfect excuse to draw the American people into the war in Europe to assist his ally Churchill. Thoughts?