During the occupation of Poland in 1939, the German army established the military district of Posen (Poznań). On November 20, this newly formed province annexed additional territory and was renamed Reichsgau Wartheland (Warthegau) and covered an area of roughly 45,000 square kilometers. In November 1939, it had a population of 4.5 million people, including 327,000 Volksdeutsche (ethnic Germans) and 366,000 Jews.
Shortly after the defeat of Poland in October 1939, the expulsion of thousands of Jews and Poles from the Wartheland to the General Government (Generalgouvernement, the zone of Nazi-occupied central Poland not formally annexed by the Reich) was initiated.
In October 1939, security police task forces (Einsatzgruppen) began to assemble the Jewish population in large cities and to establish Jewish councils that would be responsible for the implementation of decrees issued by the occupation authorities. Designated areas, referred to as ghettos, where the Jews were forced to live were established in many cities and towns throughout occupied Poland....