 Complete the following phrase:  Mieszko I, Duke of Cieszyn, the first ruler of the duchy, died in 1315 and afterwards his sons divided its land into two parts alongside Biała River: diminished Duchy of Teschen to west and Duchy of Oświęcim to east. In the middle of the 15th century Duchy of Oświęcim was bought into the Crown of the Kingdom of Poland and so the river constituted henceforth the border between Polish and the Bohemian Crown since 1526 part of the Habsburg Monarchy. Upon the First Partition of Poland in 1772 the river ceased to be a state border and continued as a regional border between Austrian Silesia to the west and Galicia to the east. After World War I and the 1919 