It was supplemented by a letter from Jacob in which the noble calls the metropolitan "the bishop of the entire Russian land... of my ancestors". The copy finishes with a passage in which Jacob is called a "Bulgarian despot". He also minted his own coins bearing the imperfect images of Saint Demetrius of Thessaloniki or Jacob himself, dressed as a warrior wearing a helmet and holding a sword. In 1263, the situation in Bulgaria was far from stable, as Constantine was facing both the threat of his predecessor Mitso Asen's throne ambitions and a large-scale Byzantine invasion. Because Constantine was unable to assist Jacob against the advancing Byzantines, Jacob sought aid from his northern neighbour, Hungarian king Stephen V. The Hungarians drove the Byzantines out of Jacob's domain and themselves invaded Byzantine-controlled territories. Rescued from the Byzantine threat, Jacob Svetoslav submitted to Hungarian suzerainty. Stephen V placed him as the ruler of the Vidin province on the Danube River, previously governed for Hungary by the then-deceased Rostislav Mikhailovich, and allowed him to retain his lands to the south. Had it not been for the appointment of Jacob Svetoslav as a Hungarian vassal at Vidin, Bulgaria would have re-established control over the city in 1263. In 1264, however, Hungary was precipitated into another civil war between Stephen V and his father Béla IV. Fearing Bulgarian retribution and lack of Hungarian support should Béla IV come out victorious, in 1265 Jacob Svetoslav changed allegiance to Bulgaria and acknowledged the authority of Constantine Tih. The two crossed the Danube in 1265 and raided the Hungarian fortresses north of the river. By the spring of 1266, however, Stephen V had established himself as the sole ruler of Hungary, and on 23 June 1266, conquered Vidin back from Jacob after a brief siege. Two waves of Hungarian raids proceeded to devastate the Vidin province and enter the possessions of Constantine. In spite of Bulgarian resistance, the Hungarians subjugated a number of cities including Pleven. Jacob Svetoslav's previous defection to Bulgarian suzerainty notwithstanding, the Hungarians restored him as the puppet ruler of the Vidin region. In 1266, he was even referred to as "Tsar of the Bulgarians" ("imperator Bulgarorum") in Hungarian sources, possibly to encourage a rivalry between Constantine and Jacob Svetoslav for the Bulgarian throne or simply to satisfy Jacob's ambitions.