The crisis that led directly to renewed European conflict in 1939 commenced with German demands against Poland, backed by threats of war, for territorial readjustments in the region of Danzig and the Baltic coast to connect East Prussia with the rest of Germany. When Warsaw refused, correctly reading Hitler's proposal as a mere prelude to further exactions, it received only hesitant promises of British and French backing. Hitler overcame the deterrent effect of this alliance on August 23 when Nazi Germany and the Soviet Union signed a nonaggression treaty that ended their interwar hostility. A secret provision of the treaty essentially divided all of Eastern Europe into Soviet and German spheres of domination. This provision signified the blessing of Soviet dictator Joseph V. Stalin for Berlin to attack Poland without fear of Soviet interference.

The Hitler-Stalin pact sealed Poland's fate and put the country in an indefensible position. On September 1, Germany hurled the bulk of its armed forces at its eastern neighbor, touching off World War II. Based on existing guarantees of security, Britain and France declared war two days later, but they gave no effective assistance to their ally. By midSeptember , Warsaw was surrounded in spite of stout resistance by outnumbered Polish forces. As Poland reeled under the assault from the west, the Soviet Union administered the coup de grace by invading from the east on September 17. By the end of the month, the "September campaign" was over, Hitler and Stalin had reached terms defining their respective gains, and the Polish lands had been subjected once more to occupation.

Data as of October 1992