The Treaty of Versailles established Gdańsk (Danzig) as a free city under the protection of the League of Nations. This solution was meant to guarantee that neither German nor Polish demands could provoke new conflicts. But frictions increased as Nazi Germany started its efforts to incorporate the free city.

After the first World War Poland re-emerged as an independent state. The Treaty of Versailles established Gdańsk (Danzig) as a free city under the protection of the League of Nations. This solution aimed to guarantee that neither German nor Polish demands could provoke new conflicts. The concept of the Free City of Gdańsk was disliked from the beginning by most of its inhabitants who, after being a part of the Prussian and later German state for a long time, claimed Gdańsk (Danzig) to be in fact German.

After about 150 years of partition the re-established Polish state got its much coveted access to the Baltic Sea to the north of Gdańsk, where a new city, Gdynia, was built as a modern sea port. As a result, East Prussia was separated from the rest of Germany by the so-called corridor. From the very beginning the political conditions in Gdańsk were unstable, one of the reasons that support for the Nazi party grew fast. In 1933 the Nazis garnered 50% of vote in the Volkstag (Parliament) elections. They formed a government which allowed a radical policy against Jews and Poles living in the territory of the Free City. Overt discrimination by the German population (a large majority) compelled many Poles to leave the city. Jews were treated worse. They were disappropriated and expelled, the beautiful Great Synagogue was destroyed in 1939. Today there is only a small Jewish community in the city. Virtually none of its members has roots in Gdańsk.

Adolf Hitler used the corridor dispute as an excuse to force the Polish state to hand over Gdańsk to Germany, but the Polish politicians refused all territorial concessions. For Hitler this created a perfect pretext to attack Poland and thereby unleash the Second World War.