Unlike the autonomous Kingdom of Croatia, medieval Transylvania was not a separate Land of the Holy Crown of Hungary, it was simply an administrative district,[1] and an integral part[2][3] of the medieval Kingdom of Hungary.
Status of Transylvania after the treaty
John Sigismund's realm in 1570
John Sigismund abdicated as King of Hungary, however, Maximilian II recognized John Sigismund's authority as "Prince of Transylvania" and, in return, John Sigismund accepted Maximilian II as King of Hungary with suzerainty over his principality.[4]
This treaty, like the earlier Treaty of Nagyvárad, endorsed the principle of a united Hungary. Partium and Transylvania were entrusted to John Sigismund Zápolya, as a vassal of King Maximilian. As mentioned above, the Zápolyas had already held the Partium, but now the Habsburgs recognized their lordship. In a sense, John Sigismund traded his royal title for territory.