Duchy of Silesia

The Duchy of Silesia (Polish: Księstwo Śląskie, German: Herzogtum Schlesien, Czech: Slezské knížectví, Silesian: Ślōnski firsztyntōm) with its capital at Wrocław was a medieval provincial duchy of Poland located in the region of Silesia.

Soon after it was formed under the Piast dynasty in 1138, it fragmented into various Silesian duchies. In 1327, the remaining Duchy of Wrocław as well as most other duchies ruled by the Silesian Piasts passed under the suzerainty of the Kingdom of Bohemia as the Duchies of Silesia. The acquisition was completed when King Casimir III the Great of Poland renounced his rights to Silesia in the 1335 Treaty of Trentschin.

Geography

During the time of its establishment, the Silesian lands covered the basin of the upper and middle Oder river. In the south the Sudetes mountain range up to the Moravian Gate formed the border with the lands of Bohemia – including Kłodzko Land – and Moravia. After a more than century-long struggle, the boundary had just been determined by an 1137 agreement with the Bohemian duke Soběslav I. In the west Lower Silesia bordered on the German March of Lusatia (later Lower Lusatia) and the former Milceni lands around Bautzen (later Upper Lusatia) with the boundary running along the Bóbr and Kwisa rivers. Silesia was limited by the Polish provinces of Greater Poland in the north and the Seniorate Province of Lesser Poland in the east, separated by the Przemsza and Biała rivers.

The boundaries varied slightly in the following decades: at least when the duchy was re-established for the sons of Władysław II the Exile in 1163 (see below), it also comprised Lubusz Land northwest of Krosno, which had been the western outpost of Greater Poland and passed to the margraves of Brandenburg in 1248. In 1177 the Polish High Duke Casimir II the Just attached the former Lesser Polish castellanies of Bytom, Oświęcim, Zator, Siewierz und Pszczyna to Upper Silesia in favour of Duke Mieszko IV Tanglefoot.