Duchy of Silesia
It also recognized Czech sovereignty over the Duchy of Silesia, which the Czech kings had controlled "de jure" with the Crown of Poland. John I relinquished the Polish crown to Casimir III in exchange for 1,200,000 Prague groschen. The Duchy of Silesia thus became part of the Czech Crown until 1742, when most of it was lost to Prussia and joined Poland after World War II in 1945. A small part is now in the Czech Republic.