April 1544, the Diet of Torda prescribed that travellers should respect the religious customs of the settlements they visited, showing that the ideas of the Reformation had spread to the whole province. The first Transylvanian Diet at which delegates from the Partium were present met in August 1544. At the Diet, Martinuzzi was made chief justice. Five counties that had previously accepted Ferdinand's ruleBereg, Szabolcs, Szatmár, Ung and Zemplénswore allegiance to John Sigismund before the end of 1555. The Ottomans laid claim to two fortresses, Becse and Becskerek (now Novi Bečej and Zrenjanin in Serbia), in early 1546. The sultan refused to include John Sigismund's realm in the peace treaty that he concluded with Ferdinand's brother, Emperor Charles V, in 1547. Both actions suggested that Suleiman intended to seize part of John Sigismund's kingdom, prompting Isabella and Martinuzzi to reopen negotiations with Ferdinand on the reunification of Hungary in 1548. Martinuzzi and Ferdinand's envoy, Nicolaus of Salm, signed a treaty in Nyírbátor on 8September 1549. According to their agreement, Isabella and John Sigismund were to abdicate in exchange for the Silesian duchies of Opole and Racibórz and 100,000 florins in compensation. Isabella refused to execute the treaty and remained in Gyulafehérvár. Martinuzzi laid siege to the town, forcing her to give up resistance in October 1550. Isabella and her supporters Péter Petrovics and Ferenc Patócsy made a new attempt to prevent the execution of the Treaty of Nyírbátor in May 1551, but Martinuzzi defeated them. Under duress, Isabella abdicated in favor of Ferdinand on John Sigismund's behalf, in return for the two Silesian duchies and 140,000 florins on 19July. Two days later, she surrendered the Holy Crown to Ferdinand's representative, Giovanni Battista Castaldo. The Diet acknowledged their abdication and swore fealty to Ferdinand on 26July. In exile Isabella and John Sigismund left Transylvania on 6August 1551, accompanied by Péter Petrovics. They settled in Kassa (now Košice in Slovakia), and moved to Opole in March 1552. Realizing that the Silesian duchies were poor, they left for Poland before the end of April. During the following years they lived in Kraków, Warsaw, Sanok, and other Polish towns. John Sigismund often went hunting for bison and regularly visited his uncle, Sigismund II Augustus, King of Poland. However, his health was delicate because he suffered from epilepsy and chronic intestinal disorders. The contemporaneous historian Ferenc Forgách, who was Isabella's implacable enemy, accused her of