September 1, 1939 - The Beginning of WWII

Hitler had been "allowed" to annex Austria in March 1938 (Anschluss) and was given part of Czechoslovakia at the September Munich Conference taking the rest in March 1939. These acquisitions had not provoked war. But when he dressed a Polish citizen in military garb and shot him at the border, then headed into Poland with a Blitzkrieg, things changed.

This time, Great Britain and France could not stand by. They issued an ultimatum and then, two days later declared war on Germany. Hitler's pact with the Soviet Union, the Nazi-Soviet Non-Aggression Pact kept the Soviet Union out of it for a little while, until it became apparent that Hitler wanted more.