Polish September CampaignThe Polish September Campaign (the German attack of Poland in September 1939 - known in Polish as the Defense War of 1939) was the military operation which started World War II.
On September 1, 1939, 04:45 local time, the German battleship Schleswig-Holstein began taking the Polish enclave Westerplatte in Gdansk by the Baltic Sea under fire. Soon, German troops attacked Poland alongside its Western, Southern and Northern borders, while German aircraft started raids on Polish cities. Despite some Polish successes in minor border battles, the German technical and numerical superiority made the Polish armies withdraw towards Warsaw. The largest battle during this campaign took place near the Bzura river west of Warsaw from September 9 to September 18 - it was the Polish attempt at a counterattack, that failed after an initial success. Warsaw itself was under siege from September 13 until its capitulation on September 28.
From September 17, 1939, the Red Army occupated the Eastern regions of Poland which have not yet been involved into military operations. The fortress Modlin north of Warsaw, capitulated on September 28. Until October 2 lasted a defence of the Hel peninsula on the Baltic Sea. The capitulation of the town of Kock (near Lublin) on October 6, after the 4-day battle, marked the end of the September Campaign.
The September Campaign was codenamed Fall Weiß ("Case White") by the German Wehrmacht. Polish historians call it Wojna obronna 1939 ("Defense War of 1939"). Tanks and aircraft (particularly fighters and bombers like the famous Junkers Ju 87 Stuka) played a major role in the fighting. Bomber aircraft also attacked whole cities (Warsaw, for instance) causing huge losses amongst the civilian population.