A sudden and rapid invasion of Poland by Nazi forces in 1939, the Polish invasion represented the first military engagement in the European theater during World War II. Poland remained under German control until 1945.
Germany's invasion of Poland on September 1, 1939 stemmed from German dictator Adolf Hitler's desire for more territory for the German state. The Treaty of Versailles (1919) that settled World War I had left Germany without the Polish Corridor, former Prussian territory taken from Germany as payment for initiating World War I. That deal irked many Germans, who later supported the Nazi regime's call for a reunification of the fatherland by attacking Poland.
The German Army had prepared for years for the attack. German industry had given the Wehrmacht (regular army) heavily armed planes capable of dropping bombs on cities and troop positions. The Wehrmacht also possessed new panzer tank divisions and other mechanized units capable of a lightning attack known as blitzkrieg. Against the overwhelming strength of the German Luftwaffe, the Polish defenders fielded seven armies and four reserve groups totaling 2 million men.
On September 1, Germany opened the attack with a daring assault by marines into a Polish fort in the harbor of Danzig. Repulsed with heavy losses, the German land attack stalled. A widespread aerial and land bombardment of cities along the Polish border immediately followed and cleared a corridor for the tanks. Planes then bombed Polish troops and communication lines. Most of the Polish Air Force was destroyed on the ground, and the planes that did make it into the air were heavily outnumbered.
German mobile mechanized units bypassed the slower Polish forces; they attacked the Polish from the rear and captured or destroyed over 200,000 Polish troops and 100,000 civilians. Germany lost only 48,000 troops. More important, approximately 787,000 Polish troops had been captured alive, which shattered the entire armed forces of the nation and left it open for Nazi domination.
Despite pockets of resistance, Poland fell to the Germans on October 6, 1939. The Nazi regime then used Poland for its war machine until 1945.