Greater Poland uprising (1918–1919)

The Greater Poland uprising of 1918–1919, or Wielkopolska uprising of 1918–1919 (Polish: powstanie wielkopolskie 1918–1919 roku; German: Großpolnischer Aufstand) or Poznań War was a military insurrection of Poles in the Greater Poland region (German: Grand Duchy of Posen or Provinz Posen) against German rule. The uprising had a significant effect on the Treaty of Versailles, which granted a reconstituted Second Polish Republic the area won by the Polish insurrectionists.

Source: Wikipedia — Greater Poland uprising (1918–1919) (CC BY-SA 4.0)