Oder-Neisse line

Wartime origins and decisions

The Oder–Neisse line was not improvised during the Second World War. The lower Oder in Silesia had been Piast Poland's western border from the 10th to the 13th century, and from around the First World War some proposed restoring it as protection against Germany. In 1918 Bolesław Jakimiak advocated a border along the Oder and Lusatian Neisse, and the idea of "Western thought" (myśl zachodnia) spread among interwar Polish nationalists. The proposal was long not seriously considered; after the war the Polish Communists, lacking their own expertise on the western border, adopted the National Democratic conception.

The Nazi occupation and genocide strengthened the demand for a secure border. At the Tehran Conference in late 1943 Stalin raised extending Poland's western frontier to the Oder; Roosevelt agreed in principle but said he could not state it publicly because of elections at home. At Yalta in February 1945 the Americans and British agreed on the Curzon line in the east and the Oder as the basic line in the west, but left open whether the eastern or western Neisse would be used. Churchill objected to the western Neisse and to the expulsion of large numbers of Germans; Stalin replied that many Germans had already fled before the Red Army.

Potsdam and the reshaping of territory and population

On 2 August 1945 the Potsdam Agreement placed the German territories east of the Oder–Neisse line under Polish administration pending the final peace settlement and decided that Germans remaining there should be expelled. The line transferred to Poland and the Soviet Union almost a quarter of Germany's territory within its 1937 boundaries, 23.8 percent of the Weimar Republic's area. Silesia, Pomerania and the southern part of East Prussia went mostly to Poland; northern East Prussia, including Königsberg (renamed Kaliningrad), went to the Soviet Union. Running some 472 km from the Czechoslovak border to the Baltic at the Oder estuary, it was the shortest possible border between Poland and Germany.

Poland received 112,000 km² of former German territory in exchange for the 187,000 km² it lost east of the Curzon line to the Soviet Union. The ensuing population transfers involved some 14 million people across Eastern Europe. Nearly all remaining Germans in the territory annexed by Poland were expelled, while Poles displaced to Germany as labourers and Poles from the annexed eastern half of the prewar republic were resettled there. The border split several cities in two: Görlitz/Zgorzelec, Guben/Gubin, Frankfurt (Oder)/Słubice and Bad Muskau/Łęknica.

Four decades of recognition

East Germany's ruling Socialist Unity Party initially rejected the line, but under Soviet pressure the GDR recognised the border with Poland in the Treaty of Zgorzelec of 6 July 1950. West Germany did not recognise that treaty as a legitimate international treaty, and the Adenauer government, in office from 1949, made clear that a reunified Federal Republic would claim all the land that had belonged to Germany as of 1 January 1937. In 1952 Stalin made permanent recognition of the Oder–Neisse line a condition for Soviet agreement to German reunification; Adenauer rejected the offer. The expellee lobby was a powerful force in West German politics, and the CDU, CSU, FDP and SPD all opposed recognition.

Willy Brandt's Ostpolitik changed West Germany's stance. In 1970 West Germany signed the Treaty of Warsaw with Poland, recognising the Oder–Neisse line as current reality and not to be changed by force, while leaving final legal settlement to a reunified Germany. In March 1990 Chancellor Helmut Kohl caused an international storm by suggesting that a reunified Germany might not accept the line; he quickly reversed himself. On 14 November 1990 reunified Germany and Poland signed the treaty confirming the border, which entered into force on 16 January 1992.