Austria, who assumed the title of Herzog von Teschen and became progenitor of the Teschen cadet branch of the Habsburg-Lorraine dynasty. While the Duchy of Teschen finally merged into the crown land of Austrian Silesia after the Revolutions of 1848, the ducal title passed down Charles' line, first to his eldest son, Archduke Albert, and then in 1895 to Albert Frederick's nephew, Archduke Frederick. With Austrian Silesia, the territory of Teschen became part of the Cisleithanian half of the Austro-Hungarian dual monarchy upon the Compromise of 1867. At the end of World War I both the crown land and the ducal title were disestablished with the dissolution of Austria-Hungary. Archduke Frederick, appointed Austrian field marshal in 1914 but soon neutralized by Chief-of-Staff Franz Conrad von Hötzendorf, found his vast possessions expropriated and retired to Magyaróvár in Hungary. Aftermath At the end of the war, local Polish and Czechoslovak self-governments were established in the territory of Cieszyn, which on 5 November 1918 signed an interim agreement under which the territory – including the town of Cieszyn itself – was divided along the Olza (Olše, Olsa) River. However, the preliminary convention failed to settle the border conflict between the newly established state of Czechoslovakia and the Second Polish Republic, which claimed further areas of the former Cieszyn duchy with a predominantly Polish-speaking population. The ongoing conflict escalated when Czechoslovak troops crossed the Olza on 23 January 1919, starting the Polish–Czechoslovak War. Clashes of arms continued until 31 January, but neither of the belligerents benefited: at the 1920 Spa Conference the division of the former duchy along the Olza was confirmed. The eastern part of Cieszyn Silesia was incorporated into the Polish Autonomous Silesian Voivodeship, while the western part (including the Zaolzie region) became part of Czechoslovakia. This was confirmed on 5 August 1920 by the Conference of Ambassadors. After World War II the remaining German population was expelled. Demographics According to the Austrian census taken in 1910, the duchy had about 350,000 inhabitants: 54.8% Polish-speaking, 27.1% Czech-speaking and 18.1% German-speaking. While the Czech population mainly settled in the western areas around Frýdek, the German population was clustered around Bielsko (). Dukes of Teschen Silesian Piasts 1290–1315 Mieszko I 1315–1358 Casimir I, son, swore homage to King John of Bohemia in 1327 1358–1410 Przemyslaus I Noszak, son 1410–1431 Boleslaus I, son 1431–1442 Wenceslaus I, became Duke of Siewierz and Bielsko 1431–1442 Wladislaus, Duke