Archduke (and future Holy Roman Emperor) Ferdinand also claimed the crown, and was elected by a rump Diet.
In 1527, Ferdinand invaded Hungary and captured Buda while Zápolya was distracted by a peasant uprising.
Zápolya's army numbered around 7,000–8,000 men, drawn mainly from eastern Hungary, Transylvania, and Serbia.
Ferdinand's Hungarian hussars then broke through Zápolya's center, seized his camp, and drove his remaining soldiers to the river Tisza.
According to a report, estimated by Pál Fodor [hu] to be from November 1527, from voivode of Moldavia Petru Rareș to the Ottoman court, Zápolya retreated to Kolosvar, from which he was driven to Tasnád by Transvlvanian forces and Székelys.