The Potsdam Conference of 1945 defined the Oder-Neisse line as the border between Germany and Poland . Millions of Germans in Silesia either fled or were expelled , and were replaced by Polish population forcibly re-settled by the Soviet Union from other regions . After 1945 and in 1946 , nearly all of the 4.5 million Silesians of German descent fled , or were interned in camps and forcibly expelled , including some thousand German Jews who survived the Holocaust and had returned to Silesia ; 634,106 Silesians died in the expulsion , nearly 14 % of the population . The newly formed Polish United Workers ' Party created a Ministry of the Recovered Territories that claimed half of the available arable land for state-run collectivized farms . Many of the new Polish Silesians who resented the Germans for their invasion in 1939 and brutality in occupation now resented the newly formed Polish communist government for their population shifting and interference in agricultural and industrial affairs
Potsdam Conference
Potsdam Conference
Silesia