The devastation of the Great War (as World War I was known at the time) had greatly destabilized Europe, and in many respects World War II grew out of issues left unresolved by that earlier conflict. In particular, political and economic instability in Germany, and lingering resentment over the harsh terms imposed by the Versailles Treaty, fueled the rise to power of Adolf Hitler and his National Socialist (Nazi) Party.

After becoming Reich Chancellor in 1933, Hitler swiftly consolidated power, anointing himself Führer (supreme leader) in 1934. Obsessed with the idea of the superiority of the "pure" German race, which he called "Aryan," Hitler believed that war was the only way to gain the necessary "Lebensraum," or living space, for that race to expand. In the mid-1930s, he began the rearmament of Germany, secretly and in violation of the Versailles Treaty. After signing alliances with Italy and Japan against the Soviet Union, Hitler sent troops to occupy Austria in 1938 and the following year annexed Czechoslovakia. Hitler's open aggression went unchecked, as the United States and Soviet Union were concentrated on internal politics at the time, and neither France nor Britain (the two other nations most devastated by the Great War) were eager for confrontation.

Outbreak of World War II (1939)
In late August 1939, Hitler and Soviet leader Joseph Stalin signed the German-Soviet Nonaggression Pact, which incited a frenzy of worry in London and Paris. Hitler had long planned an invasion of Poland, a nation to which Great Britain and France had guaranteed military support if it was attacked by Germany. The pact with Stalin meant that Hitler would not face a war on two fronts once he invaded Poland, and would have Soviet assistance in conquering and dividing the nation itself. On September 1, 1939, Hitler invaded Poland from the west; two days later, France and