From the start of his reign, Władysław Jagiełło he strove to normalize relations with the Silesian dukes, vassals of the Czech Crown, and neighbors of the Kingdom of Poland. These plans were initially disrupted by the war with Władysław Opolczyk and his nephews (1391–1396), but after it ended, relations were correct for the next two decades. Jagiełło’s wise policy towards the Silesian dukes also included his matrimonial policy, arranging marriages with representatives of the Giedyminowicz family. In the mid‑1420s, all the bordering Upper Silesian principalities were ruled by relatives of the Polish king. Despite this, the dukes of Upper Silesia remained faithful to their Czech rulers. When the Hussite Revolution broke out in Bohemia in 1419, the Silesian dukes supported Sigismund of Luxemburg, the successor of Wenceslas IV. At the same time, however, they tried to maintain proper relations with the Polish King Władysław Jagiełło, permitting – like the princes of Racibórz, Cieszyn, and Oświęcim – the Hussite legations to pass through their territories on the way to Poland and Lithuania with the offer of the crown of St. Wenceslas. The situation changed when, in September 1421 in Racibórz, Jan II Żelazny (who was married to Jagiełło’s niece Helena) imprisoned the Hussite legation sent by the Czech parliament. Despite pleas and threats from the Polish and Lithuanian sides demanding their release, the Duke of Racibórz, under great pressure, handed over the envoys to King Zygmunt. Consequently, the Silesian dukes, fearing for their principalities (at the hands of the Hussites and Poland), became closely associated with Sigismund of Luxemburg and became his allies in the conflict with Jagiełło and Witold. The culmination of these activities was that the Silesian dukes, at the beginning of 1423, joined a pact against Poland, the aim of which was its partition. However, when Sigismund of Luxemburg abruptly changed his policy and, in March 1423 in Kieżmark, concluded a treaty of friendship with King Jagiełło, the ...