The Potsdam Conference – the meeting between the leaders of the United States , Great Britain , and the Soviet Union – sanctioned the expulsion of Germans from Czechoslovakia , Poland and Hungary . With the Red Army 's advance and Nazi Germany 's defeat in 1945 , the ethnic make-up of Central and Eastern and East Central Europe was radically changed , as nearly all Germans were expelled not only from all Soviet conquered German settlement areas across Central and Eastern Europe , but also from former territories of the Reich east of the Oder-Neisse line , mainly , the provinces of Silesia , East Prussia , East Brandenburg , and Pomerania . The Soviet-established People 's Republic of Poland annexed the majority of the lands while the northern half of East Prussia was taken by the Soviets , becoming the Kaliningrad Oblast , an exclave of the Russian SFSR . The former German settlement areas were resettled by ethnic citizens of the respective succeeding state , ( Czechs , Slovaks and Roma in the former Sudetenland and Poles , Lemkos , ethnic Ukrainians in Silesia and Pomerania ) . However , some areas settled and Germanised in the course of the still form the northeastern part of modern Germany , such as the of Mecklenburg-Vorpommern , Brandenburg , Saxony and east of the in Holstein ( part of Schleswig-Holstein )
Potsdam Conference
Potsdam Conference
Ostsiedlung