The article is devoted to the events that led to the decisions about the beneficial for Poland division of the Upper Silesia in 1921. The Upper Silesia, extending over the territory of 12 320 square kilometers, is the land situated in the Upper Odra river basin. In the middle of the XIV c. it was torn away from the mother country and from 1742 it belonged to Prussia, as Regierungsbezirk Oppeln in the Province of the Upper Silesia. In 1910 as many as 2 308 000 people lived there. The most insightful research shows that Poles, dreaming about reunion with their motherland, constituted 64% of the inhabitants of this area. When Germany was defeated in World War I, it looked as if their dream might come true. Diplomatic bargaining of the victorious Coalition Powers with the defeated Germans resulted in the decision stating that the future of the Upper Silesia would be decided in a plebiscite. During the preparations for the plebiscite further diplomatic discussions lasted and staunch Polish-German political struggles took place. Additionally, regular military fights were conducted three times during the Silesian Uprisings (1919, 1920, 1921). Final decisions concerning the division of the Upper Silesia were made on 20 October 1921. They proved to be beneficial for Poland and that is why the third military confrontation went down to posterity as a victorious uprising.