The report is likely referring to the perceived expulsion of hundreds of thousands of Germans from the new Polish state after its reconstitution in 1919, and especially the "Polish Corridor" that bifurcated Germany in order to provide Polish access to the Baltic. Estimates vary--and much of this is clouded by contemporary propaganda--but hundreds of thousands of Germans certainly left the new Polish territory for a variety of reasons after 1918. Most historians of the period stress that many of these Germans likely left voluntarily, since they had no interest in living in Poland under Polish rule. This issue was nevertheless a major part of Hitler's propaganda against the so-called "Versailles system" in the interwar years, and often scurrilous stories were commonplace regarding the ostensive mistreatment of Germans forced to leave their homes after the First World War.