In two states of the Caucasian region, both under kingly rule, Christianity had gained a footing about the time of Constantine.[1140] Lazica, previously Colchis, the subject of heroic legends, and now Mingrelia, occupied the coast of the Black Sea north and south of the river Phasis. On its eastern border, watered by the Cyrus, lay Iberia, at present known as Georgia.[1141] In 522 the young king of the Lazi, alarmed lest the Persian religion should be forced on him, fled to Constantinople, and prayed for Christian baptism under the immediate countenance of the Emperor. Justin assented, and not only sustained him at the sacred font, but afterwards united him to a Roman wife, the daughter of one of the patricians of his court. Before his departure Tzathus was formally invested with ornaments and robes of state, expressly designed to denote the closeness of his relationship to Justin and to Rome.[1142] A letter of remonstrance against surreptitiously tampering with the allegiance of Persian subjects soon resulted from these proceedings; but Justin denied their political significance, and dwelt with fanatical insistence on the exigences of the faith, and the urgency of resisting heathen error.[1143] The throne of Persia was still occupied by Cavades,[1144] and that monarch now began to think seriously of going to war with Rome. On reviewing his resources he decided to enlist the Hunnish tribes, who dwelt beyond the Caucasus, as allies against the Empire. One of the most powerful chiefs agreed to his proposals, and met him by prearrangement with a large following of his nation, but during the conference messengers arrived who protested that a short time previously the Hun had been induced by a large subsidy to pledge his support to the Byzantines. “We are at peace,” said Justin, “and should not allow ourselves to be duped by these dogs.” In reply to an amicable inquiry the barbarian boasted shamelessly of the circumstance, whereupon Cavades, convinced of his treachery, at once ordered him to be cut down by his guards. Forthwith a night attack was secretly planned against his forces, who, without becoming aware of the author of the calamity, were dispersed and slain to the number of many thousands.[1145] More friendly counsels now began to prevail with the Persian, as it occurred to him that he might compose his differences with the Emperor to his own advantage. He was extremely anxious to secure the succession to his favourite son Chosroes,[1146] to the exclusion of his two elder brothers. There was reason to fear, however, that on his decease, by the intervention of the Court or the populace, one of the senior princes might be raised to the throne. Cavades, therefore, proposed to Justin that he should adopt Chosroes, considering that no party would have the temerity to dispute the tiara with a ward of the Empire. Justin and Justinian were elated at the prospect of exercising a controlling influence in Persian affairs, but the Quaestor Proclus quickly intervened, and by specious arguments, led them to see the matter in a totally different light. The adoption of the Sassanian prince, he urged with heat, would convey to him a title to inherit the crown of the Empire, Justinian might be ousted from the succession, and Justin would live in dread of being the last of the Roman emperors.[1147] An evasive course was resolved on, and a commission was dispatched to meet the Persian delegates in the vicinity of Nisibis. Chosroes himself advanced to the Tigris in the expectation of being escorted to Constantinople by the Roman envoys. The representatives of the two nations met without cordiality, and the Persians, contrary to their instructions, began by taunting the Byzantines with having usurped their rights in Lazica. The Romans then announced that the Emperor could not adopt a foreigner with legal formalities, but only by an act of arms, such as was customary among barbarians. The suggestion was taken as a deliberate insult by the Persians; the colloquy came to an end abruptly, and Chosroes returned to his father, vowing vengeance against the Romans.[1148]