The Principality of Transylvania emerged after the disintegration of the medieval Kingdom of Hungary in the 1540s. The principality included the eastern and northeastern regions of the medieval kingdom and its princes paid a yearly tribute to the Ottoman sultans. The princes were elected by the Diet, but they were to seek the Ottoman sultans' confirmation to rule the principality. The Habsburg kings of Royal Hungary regarded the principality as a part of their realm and the first rulers of the principality acknowledged the Habsburgs' claim in secret treaties in the 1570s. The Diet of Transylvania consisted primarily of the representatives of the Three Nations (that is the Hungarian noblemen, the Saxon burghers and the Székelys).