One of the significant changes that marked Vespasian’s territorial reorganization was the establishment of four legions on or near the Euphrates from its upper reaches in cappodocia to the north-eastern limits of the province of Syria at Zeugma. Vespasian established a legion each in Satala and Melitene, the two principal cities of Cappadocia. According to Suetonius, this was due to the incursions of the barbarians, presumably the Parthians, and at the same time Vespasian appointed a consular governor to replace its equestrian one.60 Vespasian’s reorganization took some years to develop and does not appear to have been as well planned as the benefit of hindsight might suggest.61 There is evidence to suggest that the reorganization that was begun in the early years of Vespasian’s reign when Caesen-nius Paetus was legatus of Syria, was refined and developed under Marcus Ulpius Traianus, the father of the future emperor and legatus of Syria from 73-77.62 Satala probably received the newly created Legio XVI Flavia Firma, while Melitene was garrisoned by Legio XII Fulminata, previously based at Rephanea in southern Syria.63 In 72/73 the client-kingdom of Commagene, between Cappadocia and the province of Syria on the right bank of the Euphrates, was added to the province of Syria. Samosata, the principal city of Commagene, received the legionary garrison of Legio VI Ferrata and perhaps part of Legio III Gallica, while the important bridge crossing at Zeugma further down the river was probably garrisoned a few years earlier by Legio IV Scythica.64
The extent of the Roman military presence on the Euphrates further south from Zeugma at the time of Vespasian’s military reorganization is difficult to establish. The discovery of a Roman milestone 27 km north-east of Palmyra dating to 75 is often used as evidence for the construction of a Roman road leading from Palmyra to the Euphrates at Sura.65 This conclusion has resulted in the assertion that Sura was garrisoned by Roman troops from the time of the Flavians, which is then used to claim that there were Roman outposts extending as far as Birtha Asporakos (Zenobia) for the protection of the province of Syria in the first century ad.66 The discovery of this milestone is the only evidence used to conclude that Sura was garrisoned at this stage, and it is clearly slender evidence on which to base an assumption about Sura’s fortification at this time.67
Commagene’s annexation and inclusion in the province of Syria, at a similar time to the transformation of Cappadocia into a military province, may be used to suggest that the stretch of the Euphrates from its upper reaches in Cappadocia to the bridge crossing at Zeugma represented a practical line designed for the defence of Syria by the end of Vespasian’s reign.68 This section of the Euphrates through Cappadocia, Commagene and Syria down to Zeugma now had four legions in fortifications close to or on its right bank - with obvious defensive benefits. While able to act in a defensive capacity, the legions strengthened Roman power across the Euphrates in Armenia and allowed attack on Parthian-influenced Osrhoene and Mesopotamia. The garrisons at Satala, Melitene and Samosata would have been particularly useful in this way, and the garrison at Zeugma guaranteed the bridge crossing into Osrhoene and Mesopotamia. The proximity of the legions to the Euphrates would also allow the quick movement of troops down the river, which is what appears to have taken place in the 160s. In Vespasian’s reorganization of territory, the role of the Euphrates had developed from symbolic boundary to a more practical and military one that assisted the Romans in later territorial expansion.
In the ongoing debate about the nature of Roman frontiers, Vespasian’s organization of the legions on the upper and middle Euphrates is often used in support of particular theories. The obvious offensive purposes of Vespasian’s actions have been rightly emphasized, but there is also some merit in the sentiment of caution expressed by Crow that ‘it is important not to predict a frontier system for the Flavian period’ because the system took some years to develop.69 The defensive purposes of military developments on the Euphrates under the Flavians have also been downplayed to an extent in the ongoing debate about the nature of Roman frontiers, but it is important not to understate the defensive capacity of four legions located in relatively close proximity to each other and to the Euphrates.
An important part of analysing the effects of Vespasian’s establishment of this concentration of troops is to consider the context of his reorganization of the provincial system in the Roman Near East.70 Along with the reorganization of Judaea, Commagene and Cappadocia, the smaller kingdoms of Chalcis and Emesa were also absorbed into Roman territory, while some suggest that Palmyra was brought firmly within Roman provincial territory under Vespasian.71 The importance of Syria and the client-kingdoms of the Euphrates to Vespasian’s elevation to the principate had demonstrated to him the potential importance of the region to the stability of his reign. Tacitus reported that after Vespasian was first hailed as Augustus at Alexandria on 1 July 69, the soldiers in Judaea did so on 3 July, while those based in the province of Syria - together with the client-kings Sohaemus of Sophene and Antiochus of Commagene - acclaimed Vespasian as Augustus on 15 July.72 Much of the momentum for Vespasian’s elevation to the principate came from the eastern provinces, which he set about to completely reorganize soon after overcoming Vitellius. With the disappearance of the client-kingdoms and the expansion of Roman provincial territory, the aim was to reduce the capacity of the
Parthians to exert influence in the territories on the Euphrates, Indeed, Josephus tells us that the reason for Commagene’s annexation under Vespasian was that its king, Antiochus, had colluded with the Parthians even after hailing Vespasian as Augustus,73 This was a considerable problem, according to Josephus, as Samosata in Commagene would allow easy passage for the Parthians in the event of a war with Rome,74 Writing approximately 20 years after these events, the poet Statius gives the impression that defence was an issue on this section of the Euphrates, particularly at Zeugma, In the Silvae, Statius says: ‘Achaemenium secludit Zeugmate Persen’ (Zeugma sets bounds to the Achaemenian Persian) and ‘Zeugma, Latinae pacis iter,,,’ (Zeugma, the way of the peace of Rome),75 When considered in the context of Vergil’s poetic use of the potential dangers posed by unrest, and invasions on the Euphrates during the civil war between Octavian and Antonius, it is possible to demonstrate a long-held concern in literature about invasions across the Euphrates, It is important, therefore, not to underestimate the defensive significance of the fortifications and legions on the Euphrates under Vespasian and his successors,
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