01 January 1919
Fights for the borders of the Second Polish Republic
The young Polish state had to fight for its new borders on its own. In the region of Greater Poland, the Poles started and won an uprising against the Germans. In the contentious territories of Upper Silesia, Varmia and Mazuria referenda were envisaged under the Treaty of Versailles. Unhappy with the solution, Silesian Poles carried out three uprisings against German authority in 1919–21. Silesia was finally divided between both countries. A Polish-Ukrainian war broke out in the east.