High Quality Content by WIKIPEDIA articles! The Principality of Transylvania was a semi-independent state under the suzerainty of the Ottoman Empire ruled by mostly Calvinist Hungarian princes. As a semi-independent state, the Principality existed from 1571 to 1711. On 29 August 1526, the army of Sultan Suleiman of the Ottoman Empire inflicted a decisive defeat on the Hungarian forces at Mohács. János Szapolyai (Zápolya) was en route to the battlefield with his sizable army but did not participate in the battle for unknown reasons. The youthful King Louis II of Hungary and Bohemia fell in battle, as did many of his soldiers. As Szapolyai was elected king of Hungary, Ferdinand from the House of Habsburg also claimed the throne of Hungary.