Original sentence: At that time it also annexed northern East Prussia, previously part of Germany, which became the Kaliningrad Oblast of the RSFSR.Most of the present-day Baltic Russians are migrants from the Soviet era and their descendants
Edited sentence: During the war Baltic region was occupied by the Germans who together with local collaborators massacred large number of Baltic Russians along with the Jews.In the aftermath Soviet Union also annexed northern East Prussia, previously part of Germany, which became the Kaliningrad Oblast of the RSFSR.Most of the present-day Baltic Russians are post 1945 migrants from the Soviet era and their descendants