Ottoman Cannon battery at the Siege of Esztergom 1543
Rather than abdicate, Zápolyai appealed to Sultan Süleyman I for aid. Süleyman recognized Zápolyai as the legitimate king and led an army into Hungary to reestablish his position. The Ottoman army easily pushed Ferdinand’s forces out of central Hungary but failed to capture Vienna (1529). A second campaign by Süleyman against Ferdinand’s capital in 1532 was stopped by the determined resistance of the town of Köszeg (Gün).
In the following years, while the two kings’ armies competed for control of the country, the Ottomans expanded their base in Hungary by occupying Slavonia and placing a garrison near Buda. As it became evident that the Ottomans alone stood to profit from the continued division of the kingdom, Ferdinand and Zápolyai worked to negotiate a settlement. By the Treaty of Várad (1538), Ferdinand recognized Zápolyai’s claim and pledged to support him with imperial forces; in return, Zápolyai named Ferdinand his heir to the throne. At Zápolyai’s death in 1540, however, his treasurer György Martinuzzi, bishop of Várad, refused to honor the agreement and had Zápolyai’s infant son elected King János II. Ferdinand’s forces were too small to occupy the kingdom and failed in two attempts to capture Buda.
In August 1541 Süleyman marched to the capital, declared himself János’s guardian, and occupied the castle. He made Buda the administrative center of a new Ottoman pashalik and gave Transylvania and the lands east of the Tisza River to János to hold as a dependent principality.
After a failed attempt by Ferdinand to recapture Buda in 1542, Süleyman carried out another campaign in Hungary, conquering Siklós, Székesfehérvár, Esztergom, and Szeged (1543).Unable to break Süleyman’s hold on the country, Ferdinand and Charles V, in the Treaty of Edirne (1547), finally extended de facto recognition of the Ottoman conquest of Hungary by agreeing to pay Süleyman an annual gift of 30,000 gold florins for possession of the northern and western portions of Hungary still in Habsburg control.
References and further reading:Perjes, Géza. The Fall of the Medieval Kingdom of Hungary:Mohács 1526-Buda 1541. Ed.Mario Fenyö. Boulder, CO: East European Monographs, 1989.