in 1548, when the ottomans gathered all their forces for an assault against persia in the ongoing ottoman–safavid war (1532–55), ferdinand and martinuzzi began negotiations to unite hungary and defend it against the ottomans. the agreement was reached on 1 august 1549 in nyírbátor. isabella would give up transylvania in exchange for opole and racibórz in silesia. ferdinand was also to provide for john sigismund, who would later marry one of his daughters. martinuzzi was to be made archbishop of gran, and to receive the cardinal's hat. isabella defended her rights and took up arms. she did not receive help from her brother sigismund ii augustus as he concluded an alliance with ferdinand so that he could quell opposition of polish nobility to his marriage to barbara radziwiłł.