After World War II approximately 200,000 Germans were deported to Germany , according to the decree of the Potsdam Conference . Under the forced exchange of population between Czechoslovakia and Hungary , approximately 73,000 Slovaks left Hungary and according to different estimations 120,500 or 45,000 Hungarians moved to present day Hungarian territory from Czechoslovakia . After these population movements Hungary became an almost ethnically homogeneous country with the exception of the Hungarian speaking Romani people
Potsdam Conference
Potsdam Conference
Treaty of Trianon