After World War II , as agreed at the Potsdam Conference ( which met from 17 July until 2 August 1945 ) , all of the areas east of the Oder – Neisse line , whether recognised by the international community as part of Germany until 1939 or occupied by Germany during World War II , were placed under the jurisdiction of other countries.The relevant paragraphs in the Potsdam Agreement are : The Allies also agreed that : because in the words of Winston Churchill The problem with the status of these territories was that the Potsdam Agreement was not a legally binding treaty , but a memorandum between the USSR , the US and the UK . It regulated the issue of the eastern German border , which was to be the Oder – Neisse line , but the final article of the memorandum said that the final decisions concerning Germany were subject to a separate peace treaty ; at which the three Allied signatories committed themselves to respect the terms of the memorandum . Hence , so long as the four Allied Powers remained committed to the Potsdam protocols , without German agreement to the Oder – Neisse line boundary there could be no Peace Treaty and no German Reunification . This treaty was signed in 1990 as the Treaty on the Final Settlement with Respect to Germany
Potsdam Conference
Potsdam Conference
Former eastern territories of Germany