'' u. '' The communist Provisional Government of Poland demanded the establishment of the post-war Polish-German border at the Oder – Neisse line , that is along the Lusatian Neisse ( Western Neisse ) , and , further north , the Oder river . Joseph Stalin indicated his support for the Polish position and the Provisional Government administered the region as soon as it was cleared of the German forces . The American and especially the British governments had a long-standing preference for the border to run further east in its southern portion , along the Nysa Kłodzka ( Eastern Neisse ) and the upper Oder rivers , which would keep a large portion of Lower Silesia and of the city of Breslau in post-war Germany . At the Potsdam Conference , the delegation of what was now the Polish Provisional Government of National Unity continued lobbying aimed at keeping all of Lower Silesia under Polish jurisdiction , rather than letting some of it be a part of the Soviet occupation zone of Germany . Taking advantage of the British delegation 's disruption by the results of the British election , the Americans engaged in dealing with the Soviets on their own . Its outcome , stated in the conference protocols , was that until the final peace settlement , the area all the way west to the Lusatian Neisse would by administered by Poland and not be a part of the Soviet zone of occupation . The planned peace conference never took place and the border has remained where it was provisionally placed in 1945 . It was confirmed in the treaties that Poland signed with West Germany in 1970 and with unified Germany in 1990
Potsdam Conference
Potsdam Conference
History of Poland (1939–1945)