After the Soviet deportation of Poles and Jews in 1939 &ndash; 1941 ( see Polish minority in Soviet Union ) , The Holocaust and the ethnic cleansing of the Polish population of Volhynia and East Galicia by Ukrainian Nationalists , the Polish population in the territories had decreased considerably . The cities of Wilno , Lwów , Grodno and some smaller towns still had significant Polish populations . After 1945 , the Polish population of the area east of the new Soviet-Polish border was in general confronted with the alternative either to accept a different citizenship or to emigrate . According to more recent research , about 3 million Roman Catholic Poles lived east of the Curzon line within interwar Poland 's borders , of whom about 2.1 million to 2.2 million died , fled , emigrated or were expelled to the newly annexed German territories . There still exists a big Polish minority in Lithuania and a big Polish minority in Belarus today . The cities of Vilnius , Grodno and some smaller towns still have significant Polish populations . Vilnius District Municipality and Sapotskin region have a Polish majority
The Holocaust
The Holocaust
Curzon Line