Royal power was only nominally restored in the lands between the Carpathian Mountains and the Lower Danube, which had been united under a voivode, known as Basarab, by the early 1320s. Although Basarab was willing to accept Charles's suzerainty in a peace treaty signed in 1324, he refrained from renouncing control of the lands he had occupied in the Banate of Severin. Charles also attempted to reinstate royal authority in Croatia and Slavonia. He dismissed the Ban of Slavonia, John Babonić, replacing him with Mikcs Ákos in 1325. Ban Mikcs invaded Croatia to subjugate the local lords who had seized the former castles of Mladen Subić without the king's approval, but one of the Croatian lords, Ivan I Nelipac, routed the ban's troops in 1326. Consequently, royal power remained only nominal in Croatia during Charles's reign. The Babonići and the Kőszegis rose up in open rebellion in 1327, but Ban Mikcs and Alexander Köcski defeated them. In retaliation, at least eight fortresses of the rebellious lords were confiscated in Slavonia and Transdanubia.