Most Germans who were not evacuated during the war were expelled from East Prussia and the other former German territories east of the Oder-Neisse line in the years immediately after the end of World War II , as agreed to by the Allies at the Potsdam conference , because in the words of Winston Churchill : After World War II , as also agreed at the Potsdam Conference ( which met from 17 July until 2 August 1945 ) , all of the area east of the Oder-Neisse line , whether recognized by the international community as part of Germany before 1933 or occupied by Germany during World War II , was placed under the jurisdiction of other countries . The relevant paragraph regarding East Prussia in the Potsdam Agreement is :
Potsdam Conference
Potsdam Conference
Evacuation of East Prussia