World War II was a global war that lasted from 1939 to 1945. Rising to power in an unstable Germany, Adolf Hitler and his National Socialist (Nazi Party) rearmed the nation and signed treaties with Italy and Japan to further his ambitions of world domination. Hitler’s invasion of Poland drove Great Britain and France to declare war on Germany, and World War II had begun. The majority of the world's countries eventually formed two opposing alliances: the Allies and the Axis.