Emperor Manuel sent an army to Hungary to help Stephen IV to regain the throne from his nephew. The young Stephen sought assistance from Vladislaus, King of Bohemia, against his uncle and the Byzantines, but the Bohemian barons refused to fight. Thereafter Stephen III sent envoys to Emperor Manuel, but "they promised nothing genuine", according to Kinnamos. The Emperor continued his campaign, but in short "realized that it was then impossible for" his protégé "to rule the Hungarians' land", and opened negotiations with Stephen III. According to their peace treaty, Emperor Manuel recognized the rule of the young Stephen, and the latter agreed to send his brother, Béla, to Constantinople. Stephen III also promised that he would allow the Byzantines to take control of Béla's duchy. Abandoned by Emperor Manuel, Stephen IV approached Frederick I, Holy Roman Emperor. Around the same time, a group of Hungarian barons and prelates sent a letter to Emperor Frederick, stating that they were willing to accept his suzerainty. Stephen III also dispatched his envoys to Frederick, who decided not to intervene, but ordered his vassalsthe King of Bohemia, the Duke of Austria, and the Margrave of Styriato keep an eye on the political situation in Hungary. King Vladislaus' son, Sviatopluk, even married Stephen III's sister, Odola. The betrothal of Stephen III to an unnamed daughter of Yaroslav Osmomysl, Prince of Halych, was also arranged around this time. Next year Stephen broke his treaty with Emperor Manuel I and "usurped Béla's heritage", according to Kinnamos. A charter of 1164 of Peter, Archbishop of Spalato (now Split, Croatia) was dated in reference to the rule of Stephen III and his ban, Ampud, suggesting that at least a part of Béla's duchyCentral Dalmatiawas under Stephen III's rule in that year. On the other hand, Stephen III's dethroned uncle invaded Sirmium where masses of the residents celebrated his return. Accompanied by the forces of King Vladislaus of Bohemia, and auxiliary troops from Austria and Halych, Stephen III launched a campaign against him. Emperor Manuel I, who was about to march against Armenian Cilicia, returned to the Danube and stormed into Hungary, advancing as far as Bács (now Bač, Serbia). He contacted King Vladislaus and persuaded him to negotiate a peace treaty with Stephen III. Abandoned by his most important ally, Stephen III was obliged to renounce Sirmium in favor of the Byzantine Empire, but only after the Emperor