Starting around 1402, priest and scholar
Jan Hus denounced what he judged as the corruption of the church and the papacy, and he promoted some of the reformist ideas of English theologian
John Wycliffe. His preaching was widely heeded in Bohemia, and provoked suppression by the church, which had declared many of Wycliffe's ideas heretical. In 1411, in the course of the
Western Schism, "
Antipope"
John XXIII proclaimed a "crusade" against King
Ladislaus of Naples, the protector of rival
Pope Gregory XII. To raise money for this, he proclaimed
indulgences in Bohemia. Hus bitterly denounced this and explicitly quoted Wycliffe against it, provoking further complaints of heresy but winning much support in Bohemia. In 1414,
Sigismund of Hungary convened the
Council of Constance to end the Schism and resolve other religious controversies. Hus went to the Council, under a safe-conduct from Sigismund, but was imprisoned, tried, and executed on 6 July 1415. The knights and nobles of Bohemia and
Moravia, who were in favour of church reform, sent the
protestatio Bohemorum to the Council of Constance on 2 September 1415, which condemned the execution of Hus in the strongest language. This angered Sigismund, who was "
King of the Romans" (head of the
Holy Roman Empire, though not yet Emperor) and brother of King
Wenceslaus of Bohemia. He had been persuaded by the Council that Hus was a heretic. He sent threatening letters to Bohemia declaring that he would shortly drown all Wycliffites and Hussites, greatly incensing the people. Disorder broke out in various parts of Bohemia and drove many Catholic priests from their parishes. Almost from the beginning, the Hussites were divided into two main groups, though many minor divisions also arose among them. Shortly before his death, Hus had accepted the doctrine of
Utraquism preached during his absence by his adherents at Prague: the obligation of the faithful to receive communion in both kinds, bread and wine (
sub utraque specie). This doctrine became the watchword of the moderate Hussites known as the Utraquists or Calixtines, from the
Latin calix (the chalice), in
Czech Kališníci (from
kalich). The more extreme Hussites became known as
Taborites (
Táborité), after the town of
Tábor, which became their centre; or Orphans (
Sirotci), a name they adopted after the death of their leader and general Jan Žižka. Under the influence of Sigismund, Wenceslaus endeavoured to stem the Hussite movement. A number of Hussites led by
Mikuláš of Hus left Prague. They held meetings in various parts of Bohemia, particularly at
Sezimovo Ústí, near the spot where the town of Tábor was founded soon afterwards. At these meetings, they violently denounced Sigismund, and the people everywhere prepared for war. In spite of the departure of many prominent Hussites, the troubles at Prague continued. On 30 July 1419, a Hussite procession headed by the priest
Jan Želivský attacked
New Town Hall in Prague and threw the king's representatives, the burgomaster, and some town councillors from the windows into the street (the first "
Defenestration of Prague"), where several were killed by the fall, after a rock was allegedly thrown from the town hall and hit Želivský. It has been suggested that Wenceslaus was so stunned by the defenestration that it caused his death on 16 August 1419. Alternatively, it is possible that he may have just died of natural causes. File:Jan Hus at the Stake.jpg|Burning of
Jan Hus at the Council of Constance,
Jena Codex, 15th century File:Jensky kodex satan prodava odpustky.jpg|The devil is selling indulgences, Jena Codex ==Outbreak of fighting==