Arab Tribesmen and Desert Frontiers in Late Antique Syria*

Chapter 16 Arab Tribesmen and Desert Frontiers in Late Antique Syria*

This chapter traces the development of the strategy employed by the Late Roman government to guard the Empire’s long frontier, which ran from Palestine to Mesopotamia along the edge of the Arabian desert, and focuses on the government’s increasing reliance on Arab allies settled within the frontier. The guardians of the eastern frontier faced difficulties not encountered in the West precisely because the frontier they had to police and defend was a desert frontier, and one that was annually crossed and re-crossed by transhumant nomads.1 Barbarian federates also came to play an extremely prominent role in the West, and it will be shown that the history of Arab groups allied to the Eastern Empire has quite a lot in common with that of Germanic federates in the service of the Western Empire, and that inadequate sources have presented modern historians of the Germanic and of the Arab allies with similar difficulties.

Diocletian’s Fortification of the Eastern Frontier2

Diocletian reorganized and strengthened the defences of the eastern prov- inces of the Empire after the crisis of the third century, which had seen Persian invasions, and the astonishing episode of the temporary conquest of much of the Near East by the client state of Palmyra. Diocletian’s reforms were in accord with Roman military traditions. He greatly increased the size of the regular army. He raised many new units3 and stationed them along the edge of the empire. The boundary of the territory under direct imperial control was now marked by a road running along the edge of the desert from the Red Sea to the

* This article was previously published in Journal of Late Antiquity (forthcoming). 1 The North African limes have presented comparable difficulties. 2 A.S. Lewin, Populi, Terre, Frontiere dell’ Impero Romano: Il Vicino Oriente nella Tarde Antichita, Catania, 2008, 9–46. 3 See A.H.M. Jones, The Later Roman Empire, Oxford, 1964, 55–60. But calculation of the actual size of Diocletian’s army is complicated by the fact that units were now much smaller than under the Early Empire, see below, n. 11.

Euphrates, a road that was used by traders, but was surely designed to help military operations. Much of the road had been constructed in the second century under the emperor Trajan, but the northernmost section was only com- pleted in the reign of Diocletian, and bore his name, the strata diocletiana. Forts garrisoned by either a cohors of infantry, or an ala of cavalry, were positioned along the road. These forts were located not at regular intervals, but at points where the migration routes of transhumant nomads crossed the frontier, and at oases and watering points within the frontier. In this arid region, intruders, whether serious invaders, casual raiders, or peaceful nomads, could only move along routes that had access to water, and it is clear that the defen- sive installations were positioned to guard precisely these routes. Research on the North African limes has focused more closely than that on the eastern frontier on how forts were situated in relation to the routes used by raiders and nomads.4 However, it is clear that the eastern Limes was not a continuous bar- rier. It could, for instance, be crossed unobserved.5 Benjamin Isaac was clearly right to describe the fortifications along the eastern limes as a military road system protected by forts.6 The alae and cohortes were the lowest ranking units of the Roman army and their officers received their commissions from the quaestor,7 while units of higher status received them from the primicerius notariorum. Regiments of the higher status, the cavalry units, equites illyricani8 and equites indigenae,9 were stationed at road junctions further in the rear. The troops stationed in the frontier region thus included a very high proportion of cavalry units. They were clearly intended to patrol long stretches of frontier, and to catch up with some highly mobile antagonists. Infantry forces, consisting of two legions in

4 See P. Trousset, “Signification de la frontière, nomades et sédentaires dans la zone du limes d’Afrique,” in W.S. Hanson and L.J.F. Keppie (eds.), Roman Frontier Studies XII, (= BAR (IS) 79, Oxford), 931–42. 5 Procopius, Aed. 3.3.9–14. 6 B. Isaac, The Limits of Empire: The Roman Army in the East, Oxford, 1992, 171. For another view, see S.T., The Roman Frontier in Central Jordan: Final Report of the Limes Arabicus Project 1986–1998, Washington, 2006. 7 As stated in Notitia Dignitatum XXVIII, p. 59.23, and most of the Eastern military lists: Et quae de minore laterculo emittuntur. On this, Jones, Later Roman Empire, 641. 8 It is generally thought that all the units of equites illyriciani were derived from one large cavalry created by the emperor Gallienus, which was broken up, probably by Diocletian, who dispersed these units along the frontier. For the argument see D. Hoffmann, Das spätrömische Bewegungsheer und die Notitia Dignitatum, vol. 1, Düsseldorf, 1969, 247–57. 9 Ariel Lewin, “Kastron Mefaa, the Equites Promoti Indigenae and the Creation of a Late Roman Frontier,” Liber Annuus 51 (2001): 293–304.