Count Petrovics first appeared on the historical scene after the death of Jovan Nenad, on the side of John Zápolya, with whom he had familial ties. In 1556, using Serbian troops, he attacked the units of Ferdinand I, Holy Roman Emperor and in doing so achieved the return to the Hungarian throne of John Sigismund Zápolya. He had considerable wealth and power in the Eastern Hungarian Kingdom during this period, one of the kingdom's wealthiest landowners as a cousin and supporter of John Zápolya, with a vast array of estates. He was a fervent supporter of the Reformation. A staunchly anti-Habsburg, pro-Ottoman magnate who was a councilor and guardian of John Sigismund Zápolya, he was an adherent of Calvinism and used his power to be a major influence in the Reformation in Hungary, driving out altars and the portraits of saints from churches. A great statesman, he was also commander of Temesvár and ban of Lugos and Karánsebes under Queen Isabella. Petrovics also had large estate in Banat, around Temesvár. He worked closely with Péter Melius Juhász, apostle and organizer of the Calvinist community in Debrecen. In November 1554 he employed famed Italian Lutheran theologianFrancesco Stancaro as the personal physician at his castle until his death in 1559. Stancaro was actually a known influence on Debrecen clergyman Tamás Arany, who became involved in a heated debate with Petrovics's Calvinist associate Peter Melius Juhász over Antitrinitarian issues; but evidently this did not affect relations between Petrovics and Francesco Stancaro as he remained in his employ until his death. Petrovics had in the previous years been pressed to leave the southern region of Temesvár, and had settled in the northern country. Thus it was in this area that he used to support Calvinist doctrines. If he had stayed in his original power base, where earlier with his help the Lutherans had already organized the first Hungarian superintendencies, then it is most probable that the Hungarian Calvinist Reformation would have begun with the Temesvár synod.
