The Polish Corridor was a strip of land granted to the newly created State of Poland by the Treaty of Versailles of 1919, connecting this new country to the Baltic Sea. It was about 150-km-long by 75-km-wide at the base, becoming narrower as it approached the sea. Having defeated the Germans in World War I, the Allied leaders arbitrarily decided to take away a chunk of territory from Germany to create Poland and its corridor, isolating East Prussia from the rest of the German territory. This infamous “peace” treaty also granted Poland full control of the sea port of Danzig, which was a city with a population composed of 85% of Germans.
The Polish Corridor created deep-seated resentment in the German people against the Allies; bitter resentment that would pave the way for Hitler’s rise to power in 1933. It would also be the main reason or rationale given by Hitler for German invasion of Poland in September 1939, which was the spark that triggered World War II, since the German population in the territories allocated to Poland, especially the Germans living in Danzig, demanded to be reincorporated to Germany. The granting of this territory and the control of the city of Danzig to Poland was one of the biggest mistakes made by the Allies right after the Great War. Also see mistakes made by US presidents. See also mistakes made by US presidents
Map of Polish Corridor