Original sentence: Many German citizens who were classified Slavic "autochthons" by Polish authorities (Slovincians, Kashubians, Upper Silesians and Masurians), – altogether 1.5 million people though theoretically should be excepted from expulsion and declared as native, sometimes were forcibly (just after the war) or willingly (starting from 1950s) included in the expulsion, because they either were considered German by the new Polish administrators or decided to leave Communist Poland
Edited sentence: Many German citizens who were Slavic autochthons in those lands, namely: Slovincians, Kashubians, and Upper Silesians and also those Slavs who were descendents of immigrants from Poland to Prussia and Holy Roman Empire (Masurians), – altogether 1.5 million people though theoretically should be excepted from expulsion and declared as native, sometimes were forcibly (just after the war) or willingly (starting from 1950s) included in the expulsion, because they either were considered German by the new Polish administrators or decided to leave Communist Poland due to the lack of democracy and economic problems of this state