These colonies were frequently visited by Christian missionaries, who endeavored to convert the native population to their faith, and incidentally also to win over the Jews. The Patriarchs of Constantinople were then hopeful of drawing the people of the Old Testament into the fold of the New. The Patriarch Photius, of the ninth century, writes thus to the Bishop of Bosporus (Kerch): "Wert thou also to capture the Judeans there, securing their obedience unto Christ, I should welcome with my whole soul the fruits of such beautiful hopes." The "Judeans," however, not only did not take the bait of the missionaries, but even managed to spoil their propaganda among the pagans. The most illustrious of all Byzantine missionaries, Cyril and Methodius, had frequent occasion to quarrel with "the Judeans, who blaspheme the Christian faith," and the boastful ecclesiastic legend asserts that the holy brothers "by prayer and eloquence defeated the Judeans [in disputes] and put them to shame" (about 860). The struggle between the Christian missionaries and the Jews during that period had for its object the Khazar nation, part of whom had embraced Judaism. 2. THE KINGDOM OF THE KHAZARS While Byzantium was pressing on the Euxine colonies from the west, endeavoring to draw them, together with the adjoining lands of the Slavs, into the sphere of Christian civilization, a new power from the east, from the Caucasus and the Caspian region, came rushing along in the same direction. We refer to the Khazars, or Kazars.[6] Forming originally a conglomerate of Finno-Turkish tribes, the warlike Khazars appeared in the Caucasus during the "migration of nations," and began to make inroads into the Persian Empire of the Sassanids, often acting as the tools of Persia's rival, Byzantium. The great Arabic conquests of the seventh century and the rise of the powerful Eastern Caliphate checked the movement of the Khazars towards the East, and turned it westward, to the shores of the Caspian Sea, the mouths of the Volga and the Don, the Byzantine colonies on the Black and Azov Seas, and, in particular, the flourishing region of Tauris. At the mouth of the Volga, where the mighty river joins the Caspian Sea, near the present city of Astrakhan, arose the kingdom of the Khazars with its capital Ityl, the name originally designating the river Volga. From there the bellicose Khazars made constant raids upon the Slavonian tribes far and near, to the very gates of Kiev, forcing them to become their tributaries.