Some years afterwards (293) a new ruler, Narseh, son of king Shapur, ascended the throne of Ctesiphon, and declared war on the Romans in the year 296 for the possession of Mesopotamia and Armenia.[120] Diocletian, who then had the supreme conduct of the empire generally, and of the East in particular, entrusted the management of the war to his imperial colleague Galerius Maximianus, a rough but brave general. The beginning was unfavourable. The Persians invaded Mesopotamia and reached as far as Carrhae; the Caesar led against them the Syrian legions over the Euphrates at Nicephorium; between these two positions the armies encountered each other, and the far weaker Roman force gave way. It was a hard blow, and the young general had to submit to severe reproaches, but he did not despair. For the next campaign reinforcements were brought up from the whole empire, and both rulers personally took the field; Diocletian took his position in Mesopotamia with the chief force, while Galerius, reinforced by the flower of the Illyrian troops that had in the meantime come up, met, with a force of 25,000 men, the enemy in Armenia, and inflicted on him a decisive defeat. The camp and the treasure, nay, even the harem, of the great-king fell into the hands of the warriors, and with difficulty Narseh himself escaped from capture. In order to recover the women and the children the king declared himself ready to conclude peace on any terms; his envoy Apharban conjured the Romans to spare the Persians, saying that the two empires, the Roman and the Parthian, were, as it were, the two eyes of the world, and neither could dispense with the other. It would have lain in the power of the Romans to add one more to their Oriental provinces; the prudent ruler contented himself with regulating the state of possession in the north-east. Mesopotamia remained, as a matter of course, in the Roman possession; the important commercial intercourse with the neighbouring foreign land was placed under strict state-control and essentially directed to the strong city of Nisibis, the basis of the Roman frontier-guard in eastern Mesopotamia. The Tigris was recognised as boundary of the direct Roman rule, to such an extent, however, that the whole of southern Armenia as far as the lake Thospitis (lake of Van) and the Euphrates, and so the whole upper valley of the Tigris, should belong to the Roman empire. This region lying in front of Mesopotamia did not become a province proper, but was administered after the previous fashion as the Roman satrapy of Sophene. Some decades later the strong fortress of Amida (Diarbekir) was constructed here, thenceforth the chief stronghold of the Romans in the region of the upper Tigris. At the same time the frontier between Armenia and Media was regulated afresh, and the supremacy of Rome over that land, as over Iberia, was once more confirmed. The peace did not impose important cessions of territory on