The study introduces the figure of Jan Železný - the bishop of Litomyšl (1388-1418) and Olomouc (1416/18-1430), administrator of the Prague diocese (1421-1430) and Cardinal Priest of the Title of St Cyriac (1426-1430), who is one of the most famous Bohemian opponents of Master Jan Hus and the Bohemian Reformation. Emphasis is placed on following the relationship of Jan Železný to King of Hungary, later of the Romans and Bohemia, Sigismund. This relationship began deep in the reign of Wenceslas IV, when Jan Železný was among the noble opposition to Wenceslas and therefore cooperated with the King of Hungary, but it acquired a new intensity in the context of the death of Jan Hus and particularly in connection with the wars of Sigismund against the Hussites. In the first half of the 1420s, Jan Železný was an important link in Sigismund´s military coalition, but in the second half of the 1420s he had to go into exile at Sigismund´s court and following the intentions of Pope Martin V he attempted to stop the new course of Sigismund´s Hussite policy., Petr Elbel., and Obsahuje seznam pramenů a odkazy pod čarou