The Battle of (the) Annaberg (Polish: Bitwa o Górę Św. Anny) was the biggest battle of the Silesian Uprisings. The battle, which took place between May 21–26, 1921, was fought at the Annaberg (Polish: Góra Św. Anny), a strategic hill near the village of Annaberg O.S. (Góra Świętej Anny), located southeast of Oppeln (Opole) in Upper Silesia, Weimar Germany. After the hill had been captured by irregular Polish-Silesian units in the Third Silesian Uprising, German Freikorps pushed the Polish forces back. The final border was determined by political and diplomatic efforts.