John Zápolya
The throne of Hungary became the subject of a dynastic dispute between Ferdinand and John Zápolya from Transylvania. Suleiman had promised to make Zápolya the ruler of all Hungary. Ferdinand set out to enforce his claim on Hungary and captured Buda from John Zápolya in 1527, only to relinquish his hold on it in 1529 when an Ottoman counter-attack stripped Ferdinand of all his territorial gains during 1527 and 1528. The siege of Vienna in 1529 was the first attempt by Suleiman the Magnificent to capture the Austrian capital. This siege signalled the pinnacle of Ottoman power and the maximum extent of Ottoman expansion in central Europe.