After the invasion of Poland, the conquered territory of Greater Poland was split between four Reichsgaue and the General Government area (further east). The Militärbezirk Posen was created in September 1939, and on 8 October 1939 annexed by Germany, as the Reichsgau Posen, with SS Obergruppenfuhrer Arthur Greiser as the only Gauleiter. The name Reichsgau Wartheland was introduced on 29 January 1940.