Before ten years had elapsed, their camps were seated on the Danube and the Elbe, many Bulgarian and Slavonian names were obliterated from the earth, and the remainder of their tribes are found, as tributaries and vassals, under the standard of the Avars. The chagan, the peculiar title of their king, still affected to cultivate the friendship of the emperor; and Justinian entertained some thoughts of fixing them in Pannonia, to balance the prevailing power of the Lombards. But the virtue or treachery of an Avar betrayed the secret enmity and ambitious designs of their countrymen; and they loudly complained of the timid, though jealous, policy of detaining their ambassadors, and denying the arms which they had been allowed to purchase in the capital of the empire. Perhaps the apparent change in the dispositions of the emperors may be ascribed to the embassy which was received from the conquerors of the Avars. The immense distance, which eluded their arms, could not extinguish their resentment; the Turkish ambassadors pursued the footsteps of the vanquished to the Jaik, the Volga, Mount Caucasus, the Euxine, and Constantinople, and at length appeared before the successor of Constantine, to request that he would not espouse the cause of rebels and fugitives. The emperor renounced, or seemed to renounce, the fugitive Avars, but he accepted the alliance of the Turks; and the ratification of the treaty was carried by a Roman minister to the foot of Mount Altai. Under the successors of Justinian, the friendship of the two nations was cultivated by frequent and cordial intercourse.[c] RELATIONS OF THE ROMAN EMPIRE WITH PERSIA [Sidenote: [400-527 A.D.]] The Asiatic frontier of the Roman Empire was less favourable for attack than defence. The range of the Caucasus was occupied, as it still is, by a cluster of small nations of various languages, strongly attached to their independence, which the nature of their country enabled them to maintain amidst the wars and conflicting negotiations of the Romans, Persians, and Huns, by whom they were surrounded. The kingdom of Colchis (Mingrelia) was in permanent alliance with the Romans, and the sovereign received a regular investiture from the emperor. The Tzans, who inhabited the mountains about the sources of the Phasis, enjoyed a subsidiary alliance with Justinian until their plundering expeditions within the precincts of the empire induced him to garrison their country. Iberia, to the east of Colchis, the modern Georgia, formed an independent kingdom under the protection of Persia.