The Duke of Silesia was the title of sons and descendants of the Polish Duke Bolesław III Wrymouth. In accordance with the last will and testament of Bolesław, upon his death his lands were divided into four or five hereditary provinces distributed among his sons, and a royal province of Kraków reserved for the eldest, who was to be High Duke of all Poland. This was known as the fragmentation of Poland. Subsequent developments lead to further splintering of the duchies.
At the beginning of the 14th century, fourteen independent Duchies existed in Silesia: Brzeg, Wrocław, Świdnica, Jawor, Ziębice, Głogów, Ścinawa, Żagan and Oleśnica in Lower Silesia; Koźle, Cieszyn, Bytom, Niemodlin, Opole, Strzelce, Racibórz and Opava in Upper Silesia and the ecclesiastical Duchy of Nysa. Between 1327 and 1329 most dukes accepted the overlordship of Bohemian king John of Bohemia, who acquired the right of succession for all of these duchies. In the coming centuries all branches of the Silesian Piasts died out, and with the death of George William, Duke of Liegnitz the dynasty ceased to exist.
