Stefan Dragutin, who controlled the Szerémség, Macsó and other regions along the southern borders of Hungary, died in 1316. Charles confirmed the right of Stefan Dragutin's son, Vladislav, to succeed his father and declared Vladislav the lawful ruler of Serbia against Stefan Uroš II Milutin. However, Stefan Uroš II captured Vladislav and invaded the Szerémség. Charles launched a counter-campaign across the river Száva and seized the fortress of Macsó. In May 1317, Charles's army suppressed the Abas' revolt, seizing Ungvár and Nevicke Castle (present-day Uzhhorod and Nevytsky Castle in Ukraine) from them. After that, Charles invaded Matthew Csák's domains and captured Komárom (now Komárno in Slovakia) on 3 November 1317. After his uncle, King Robert of Naples, granted the Principality of Salerno and the domain of Monte Sant'Angelo to his brother (Charles's younger uncle), John, Charles protested and laid claim to those domains, previously held by his father. After Charles neglected to reclaim Church property that Matthew Csák had seized by force, the prelates of the realm made an alliance in early 1318 against all who would jeopardize their interests. Upon their demand, Charles held a Diet in summer, but refused to confirm the Golden Bull of 1222. Before the end of the year, the prelates made a complaint against Charles because he had taken possession of Church property. In 1319, Charles fell so seriously ill that the pope authorized Charles's confessor to absolve him from his all sins before he died, but Charles recovered. In the same year, Dózsa Debreceni, whom Charles had made voivode of Transylvania, launched successful expeditions against Ladislaus Kán's sons and their allies, and Charles's future Judge royal, Alexander Köcski, seized the Kőszegis' six fortresses. In summer, Charles launched an expedition against Stefan Uroš II Milutin, during which he retook Belgrade and restored the Banate of Macsó. The last Diet during Charles's reign was held in 1320; following that, he failed to convoke the yearly public judicial sessions, contravening the provisions of the Golden Bull. Matthew Csák died on 18 March 1321.