So great was the blow inflicted on the Caliph by the entire failure of his army before Constantinople, that he was glad to conclude an ignominious peace with the emperor, by which he engaged to pay 3000 pounds of gold to Constantine, and to send him fifty Arab horses for every year that the treaty lasted (678). The fidelity of the East-Romans to the house of Heraclius was thus justified by the victory of Constantine; it is a pity that only a very meagre account of his campaign has come down to us, owing to the dearth of chroniclers in the seventh century. We know, however, that the fame of his triumph went all over Europe, and that ambassadors came from the Avars, the Lombards, and even the distant Franks to congratulate him on beating off an attack which had threatened serious consequences to the whole of Christendom. [Sidenote: The Bulgarians.] For the remainder of his reign Constantine enjoyed a well-earned peace, disturbed only by some slight bickering with a new enemy, the Bulgarians. This Ugrian tribe, who had dwelt for the last two centuries beyond the Danube, crossed the river in the end of Constantine’s reign, and threw themselves upon the Slavonic tribes who held Moesia. They subdued the Slavs without much difficulty, and defeated a Roman army which Constantine led by sea to the mouth of the Danube. Recognising that it was impossible to reconquer the long-lost Moesia, the emperor made peace with Isperich, the Bulgarian king, and allowed him to settle without further opposition in the land between the Danube and the Balkans, where the Slavs had hitherto held possession (679). A new Bulgarian nation was gradually formed by the intermixture of the conquering tribe and their subjects: when formed, it displayed a Slavonic rather than a Ugrian type, and spoke a Slavonic not a Ugrian tongue. The later years of Constantine V. were better known to contemporaries as the time of the holding of the council of Constantinople, than as the time of the foundation of the new Bulgarian kingdom. To settle the dispute on the divine and human wills of Christ, the emperor summoned an œcumenical synod, at which the Western churches were well represented. It finally condemned the Monothelite heresy, which for the future ceased to be the great question debated between the churches (680-1). But a new controversy, that on Iconoclasm, was ere long to break out.