the Ottoman offensive on eastern Venetian territories. The offensive resumed after the Ottoman victory of Preveza (1538), fought between an Ottoman fleet commanded by Hayreddin Barbarossa and that of a Christian alliance assembled by Pope Paul III. 1462–1483: Wallachian and Moldavian campaigns In 1462, Mehmed II was driven back by Wallachian prince Vlad III Dracula in the Night Attack at Târgovişte. However, the latter was imprisoned by Hungarian king Matthias Corvinus. This caused outrage among many influential Hungarian figures and Western admirers of Vlad's success in the battle against the Ottoman Empire (and his early recognition of the threat it posed), including high-ranking members of the Vatican. Because of this, Matthias granted him the status of distinguished prisoner. Eventually, Dracula was freed in late 1475 and was sent with an army of Hungarian and Serbian soldiers to recover Bosnia from the Ottomans. There he defeated Ottoman forces for the first time. Upon this victory, Ottoman forces entered Wallachia in 1476 under the command of Mehmed II. Vlad was killed and, according to some sources, his head was sent to Constantinople to discourage the other rebellions. (Bosnia was completely added to Ottoman lands in 1482.) The Turkish advance was temporarily halted after Stephen the Great of Moldavia defeated the armies of the Ottoman Sultan Mehmed II at the Battle of Vaslui in 1475, one of the greatest defeats of the Ottoman Empire until that time. Stephen was defeated the next year at Războieni (Battle of Valea Albă), but the Ottomans had to retreat after they failed to take any significant castle (see siege of Neamț Citadel) as a plague started to spread in the Ottoman army. Stephen's search for European assistance against the Turks met with little success, even though he had "cut off the pagan's right-hand", as he put it in a letter. 1526–1566: Conquest of the Kingdom of Hungary After the Ottoman victory in the Battle of Mohács in 1526, only the southwestern part of the Kingdom of Hungary was actually conquered. The Ottoman campaign continued between 1526 and 1556 with small campaigns and major summer invasions – troops would return south of the Balkan Mountains before winter. In 1529, they mounted their first major attack on the Austrian Habsburg monarchy, attempting to conquer the city of Vienna (siege of Vienna). In 1532, another attack on Vienna with 60,000 troops in the main army was held up by the