The more westerly part of East and West-Prussia , Pomerania ,Silesia and eastern part of Brandenburg were given by the Soviet Union to Polish administration. Autochthones is the name used by Polish authorities to classify a group of ethnic Germans ,who had their homeland forcibly taken over by Soviet Union military by the end of World War II and years after. The majority of eastern Germans was killed or ousted . Some refugees returned and were able to remain, despite greatest hardships . They were forced to become Polish. Of the 1 1/2 million people classified by Poland as Autochthones a small percentage were Kassubians from Pomerania.
The following website gives some details on the Germans classified by Polish authorities as Autochthones plus other nationalities in the current Poland : http://src-h.slav.hokudai.ac.jp/publictn/acta/16/alfred/alfred-1.html