At the 1945 Potsdam Conference following the German defeat in World War II , Poland 's borders were reorganized at the insistence of the Soviet Union , which occupied the entire area . Territories east of the Oder-Neisse line , including Danzig , were put under Polish administration . The Potsdam Conference did not debate about the future of the territories that were part of western Poland before the war , including the corridor . It automatically became part of the reborn state in 1945
Potsdam Conference
Potsdam Conference
Polish Corridor