Gyulafehérvár from 8 to 17 March. The growing influence of the Anti-Trinitarians on John Sigismund became obvious in 1569. After Péter Károlyi, a Calvinist cleric, complained about John Sigismund's bias, John Sigismund accused the Calvinist bishop, Melius, of having persecuted non-Calvinist priests, stating that Melius "should not play the pope". The largest debate between the Calvinist and Anti-Trinitarian, or Unitarian, theologians took place in Nagyvárad from 20 to 25 October 1569. Although neither side was declared winner, after the debate John Sigismund accepted Anti-Trinitarian ideas, which made him the only Unitarian monarch in history. We wish that in our freedom shall reign. We know furthermore that faith is a gift from God and that conscience cannot be constrained. And if [Peter Melius Juhász] does not abide by this, he may go to the other side of the Tisza.|John Sigismund's words to Péter Károlyi After John Sigismund's conversion, most of his courtiers also adhered to Unitarianism. According to historian Gábor Barta, political factors also contributed to John Sigismund's conversion, because he "found in [Anti-Trinitarianism] the means through which he could express both his adherence to the Christian world and the distance from it". István Keul says that the simplicity of the idea that "There is but one God!" also contributed to the spread of Unitarianism, especially among the Székely villagers and the townspeople of Kolozsvár. A religious enthusiast, György Karácsony, stirred up many peasants in Partium to wage holy war against the Ottomans in 1569. They marched against Debrecen, but the neighboring noblemen routed them near the town in early 1570. Prince of Transylvania Negotiations between John Sigismund and Maximilian II concluded with the Treaty of Speyer, signed on 16August 1570. John Sigismund acknowledged Maximilian II as the sole king of Hungary and abandoned his own royal title. Instead, he adopted the new title "Prince of Transylvania and Lord of Parts of the Kingdom of Hungary", also confirming that his realm was part of the Kingdom of Hungary and would revert to Maximilian II or Maximilian II's heir after John Sigismund's death. John Sigismund, now gravely ill, ratified the treaty on 1December. The last Diet to meet during his reign confirmed the decrees of previous Diets enhancing religious freedom. He died in Gyulafehérvár on 14March 1571, a few days after Maximilian II had ratified the Treaty of Speyer. The Transylvanian lords kept his death secret for days. He was buried in