The Hungarian campaign of 1527–1528 was launched by Ferdinand I, Archduke of Austria and King of Hungary and Bohemia against the Ottoman Turks. Following the Battle of Mohács, the Ottomans were forced to withdraw as events elsewhere in their now massive Empire required the Sultan's attention. Seizing upon their absence, Ferdinand I attempted to enforce his claim as King of Hungary. In 1527 he drove back the Ottoman vassal John Zápolya and captured Buda, Gyor, Komárno, Esztergom, and Székesfehérvár by 1528. Meanwhile, the Ottoman Sultan, Suleiman the Magnificent, took no action at this stage despite the pleas of his vassal.