According to the Potsdam Conference in 1945 after World War II , the German part of Prussia was divided between Poland and the Soviet Union , which divided its part further between the Lithuanian SSR and the Russian SFSR . Warmia and Masuria are now in Poland , while northern East Prussia ( minus the former Memelland which is now the Klaipėda region of Lithuania ) forms the Kaliningrad Oblast exclave of the Russian Federation . Beginning in 1944 with the westward advance of Soviet troops the native German-speaking population was subject to forced relocation or reeducation . For additional information , see Expulsion of Germans from Poland
Potsdam Conference
Potsdam Conference
Prussia (region)