The flight and expulsion of Germans from Poland was the largest of a series of flights and expulsions of Germans in Europe during and after World War II. The German population fled or was expelled from all regions which are currently within the territorial boundaries of Poland: including the former eastern territories of Germany annexed by Poland after the war and parts of pre-war Poland; despite acquiring territories from Germany, the Poles themselves were also expelled from the former eastern territories of Poland annexed by the Soviet Union. West German government figures of those evacuated, migrated, or expelled by 1950 totaled 8,129,800 (6,981,000 from the former eastern territories of Germany; 290,800 from Danzig, 688,000 from pre-war Poland and 170,000 Baltic Germans resettled in Poland during the war). Research by the West German government put the figure of Germans emigrating from Poland from 1951 to 1982 at 894,000; they are also considered expellees under German Federal Expellee Law.
The German population east of Oder-Neisse was estimated at over 11 million in early 1945. The first mass flight of Germans followed the Red Army's advance and was composed of both spontaneous flight driven by Soviet atrocities, and organised evacuation starting in the summer of 1944 and continuing through to the spring of 1945. Overall about 1% (100,000) of the German civilian population east of the Oder–Neisse line perished in the fighting prior to the surrender in May 1945. In 1945, the eastern territories of Germany as well as Polish areas annexed by Germany were occupied by the Soviet Red Army and communist Polish military forces. German civilians were also sent as "reparation labor" to the USSR. The Soviet Union transferred former German territories in the east of the Oder–Neisse line to Poland in July 1945. In mid-1945, 4.5 to 4.6 million Germans remained on the territories that were given under Polish control pending a final peace conference with Germany, which eventually never took place.