Hitler begins an invasion of Russia, violating his own strategy. England survives losses in Greece and Crete, but wins against the Italians in Libya until the Germans arrive. At the end of the year, attacked by the Axis, the United States joins the war.
War engulfs the Pacific when Japan attacks the US Pacific Fleet at Pearl Harbor. Attacks the same day on Guam, Wake, Philippines, Singapore, and many other places. The Allies were not prepared for many reasons, including underestimating the size of the Japanese Army. The Sino-Japanese War had expanded beyond China to the whole world.