A war, however, appears certainly to have occupied Chosroes about this period on his north-eastern frontier.  The Turks had recently been advancing in strength and drawing nearer to the confines of Persia.  They had extended their dominion over the great Ephthalite kingdom, partly by force of arms, partly through the treachery of Katulphus, an Ephthalite chieftain; they had received the submission of the Sogdians, and probably of other tribes of the Transoxianian region, previously held in subjection by the Ephthalites; and they aspired to be acknowledged as a great power, the second, if not the first, in this part of Asia.  It was perhaps rather with the view of picking a quarrel than in the hope of any valuable pacific result, that, about the close of A.D. 567, Diza-bul, the Turkish Khan, sent ambassadors to Chosroes with proposals for the establishment of free commercial intercourse between the Turks and Persians, and even for the conclusion of a treaty of friendship and alliance between the two nations.  Chosroes suspected the motive for the overture, but was afraid openly to reject it.  He desired to discourage intercourse between his own nation and the Turks, but could devise no better mode of effecting his purpose than by burning the Turkish merchandise offered to him after he had bought it, and by poisoning the ambassadors and giving out that they had fallen victims to the climate.  His conduct exasperated the Turkish Khan, and created a deep and bitter hostility between the Turks and Persians.  It was at once resolved to send an embassy to Constantinople and offer to the Greek emperor the friendship which Chosroes had scorned.  The embassy reached the Byzantine court early in A.D. 568, and was graciously received by Justin, the nephew of Justinian, who had succeeded his uncle on the imperial throne between three and four years previously.  A treaty of alliance was made between the two nations; and a Roman embassy, empowered to ratify it, visited the Turkish court in the Altai mountains during the course of the next year (A.D. 569), and drew closer the bonds of friendship between the high contracting powers.  But meanwhile Dizabul, confident in his own strength, had determined on an expedition into Persia.  The Roman ambassador, Zemarchus, accompanied him on a portion of his march, and witnessed his insulting treatment of a Persian envoy, sent by Chosroes to meet him and deprecate his attack.  Beyond this point exact information fails us; but we may suspect that this is the expedition commemorated by Mirk-hond, wherein the Great Khan, having invaded the Persian territory in force, made himself master of Shash, Ferghana, Samarkand, Bokhara, Kesh, and Nesf, but, hearing that Hornisdas, son of Chosroes, was advancing against him at the head of a numerous army, suddenly fled, evacuating all the country that he had occupied, and retiring to the most distant portion of Turkestan.  At any rate the expedition cannot have had any great success;