moved down the Tigris, taking Ctesiphon, and gazing onwards to the ruins of Babylon before returning to Roman territory via the Euphrates. No source ever specifically claims that Ctesiphon was sacked, but it is assumed to have been, primarily due to the seizure of Narseh's wife and harem. Peace negotiations Narseh had previously sent an ambassador to Galerius to plead for the return of his wife and children, but Galerius had dismissed this ambassador, reminding him of how Shapur had treated Valerian. The Romans, in any case, treated Narseh's captured family well perhaps seeking to evoke comparisons to Alexander and his beneficent conduct towards the family of Darius III. Peace negotiations began in the spring of 299, with both Diocletian and Galerius presiding. Their magister memoriae (secretary) Sicorius Probus was sent to Narseh to present terms. The conditions of the Peace of Nisibis were heavy: Persia would give up territory to Rome, making the Tigris the boundary between the two empires. Further terms specified that Armenia was returned to Roman domination with the fort of Ziatha as its border; Caucasian Iberia would pay allegiance to Rome under a Roman appointee; Nisibis, now under Roman rule, would become the sole conduit for trade between Persia and Rome; and Rome would exercise control over the five satrapies between the Tigris and Armenia: Ingilene, Sophanene (Sophene), Arzanene (Aghdznik), Corduene, and Zabdicene (near modern Hakkâri, Turkey). These regions included the passage of the Tigris through the Anti-Taurus range; the Bitlis pass, the quickest southerly route into Persian Armenia; and access to the Tur Abdin plateau. With these territories, Rome would have an advance station north of Ctesiphon, and would be able to slow any future advance of Persian forces through the region. Under the terms of the peace, Tiridates would regain both his throne and the entirety of his ancestral claim, and Rome would secure a wide zone of cultural influence in the region. Because the empire was able to sustain such constant warfare on so many fronts, it has been taken as a sign of the essential efficacy of the Diocletianic system and the goodwill of the army towards the tetrarchic enterprise. Rule as Augustus After the abdication of Diocletian in 305 and the elevation of Constantius I and Galerius to the rank of Augustus, two new Caesars were required to take their place. The two persons whom Galerius promoted to the rank