Following World War I, the Treaty of Versailles (1918) declared Danzig to be a free city administered by Poland and the League of Nations. Germany resented the loss of this largely German city. Hitler was determined to overturn the military and territorial provisions of the Versailles treaty. After invading Poland in September 1939, Nazi Germany annexed Danzig.
In the 1919 Treaty of Versailles, the victorious powers of World War I (the United States, Great Britain, France, and other allied states) imposed punitive territorial, military, and economic treaty terms on defeated Germany. One provision required Germany to cede West Prussia to the newly reconstructed state of Poland. Danzig, largely an ethnically German city, became a "free city" under the protection of the League of Nations (the worldwide organization of states established by the treaty), but with special administrative ties to Poland.
Hitler was determined to overturn the military and territorial provisions of the Versailles treaty and include ethnic Germans in the Reich. In preparation for war with Poland, in the spring of 1939 Hitler demanded the annexation of the Free City of Danzig to Germany and extraterritorial rail access for Germany across the "Polish Corridor," the Polish frontier to East Prussia.
Britain and France were convinced by the German occupation of Bohemia and Moravia in March 1939 (in violation of the 1938 Munich Pact) that Hitler could not be trusted to negotiate in good faith. They therefore guaranteed the integrity of Polish territory against German aggression. Germany invaded Poland on September 1, 1939. Britain and France declared war on Germany on September 3. With that, the German invasion of Poland became World War II.
Danzig Within weeks the Poles surrendered. Germany annexed most of western Poland and Danzig. In September 1939, the Germans constructed the Stutthof camp in a wooded area west of Stutthof, a town about 22 miles east of Danzig.
Originally, Stutthof was a civilian internment camp under the Danzig police chief. In November 1941, it became a security police holding center for political prisoners and persons accused of violating labor discipline. Finally, in January 1942, Stutthof became a concentration camp under the jurisdiction of the SS Economic-Administrative Main Office. More than 100 Stutthof subcamps were established throughout northern and central Poland, including in Danzig itself.
After World War II, Danzig and its environs became part of Poland. The German population either fled or was expelled. The Poles renamed the city Gdansk.