What were the military, political, economic, and social functions of the late Roman system of frontiers?

It may be useful; to begin this examination of the late Roman system of frontiers by illuminating what is meant by the term ‘barbarian’. Originally, a Greek word, ‘barbaros’, it most obviously referred to foreigners in an ethnocentric and political sense for both the Greeks and the Romans. It later took on an ethical consideration, as a pejorative which labelled the recipient as uncivilised.[1] Roman ’barbarian’ policy was directed at those peoples who lived near and around the borders of the Roman Empire. Sociologically and psychologically it could be posited that the Roman Empire needed to define what it was to be Roman by defining what was not – the ‘barbarian’.

Frontiers and ‘Barbarian Policy’ under the Roman Empire in the Fourth Century

The limes of the Roman Empire did not refer to a military frontier, according to Whittaker; but by the fourth century AD it did denote the borderlands.[2] The beginning of this century sees Diocletian and his tetrarchy reigning over the Roman Empire. It was a new power structure designed to share the workload of ruling a territory which:

 “stretched over six thousand kilometres from the deserts of the Negev and Jordan” to the… Caucasus, …Wallachia, the Rhine, … Northumberland and … Algeria”.[3]

Diocletian reordered the Roman defence of the frontiers by increasing legions and auxiliary forces on the front lines.[4] The evidence contained in the Notitia Dignitatum, although composed in 395, is interpreted by Whittaker as showing increases of some two hundred and eighty thousand soldiers on the frontiers during this century.[5] Mitchell declares that for much of the fourth century, “the Roman state was ruled by warrior emperors” who campaigned against both internal rivals and foreign enemies.[6] The battlelines, however, were not always clearly demarcated along the lines of Roman versus ‘barbarian’. Goffart argues that the late Roman Empire:

 “continually explored how best to employ the valuable and sometimes dangerous human resource on its doorstep”.[7]

The frontiers of the Empire were hotbeds of economic, political and social activity; not just military outposts.

Our main, contemporary, ancient source for imperial action on the frontiers in the latter half of the fourth century is Ammianus Marcellinus; an aide to magister equitum Ursicinus during the reign of Constantius II.[8] It is the views of Ammianus which enliven our conceptions of this period. Ammianus essentially portrays Roman frontier policy as defensive; keeping the ‘barbarians’ out by whatever means; by force and by diplomatic guile when necessary.[9]

The Verona List, a fourth century administrative document, enjoins a catalogue of the Roman provinces with one from the ‘barbarian peoples who multiplied under the emperors’.[10] Goffart sees this as an example of ‘barbarians’ being a daily reality for Romans during late antiquity, and they were also considered “worthy partners” involved in common enterprise by the imperial government. This view contrasts the more traditional ‘fall of Rome’ theory pursued by historians like A. H. M. Jones, who argued that invading Germanic forces from the north were the determining factor in western Rome’s decline.[11]

The frontiers of the eastern Empire were, in Whittaker’s view, more stable due to the presence of the Sassanian Empire; somewhat like the cold war stalemate of the late twentieth century.[12] Constantius was involved in diplomatic efforts in Armenia to ensure pro-Roman leadership in that kingdom.[13] Military actions did occur in 337/8, 344, 346 and 350 when Constantius directed Roman forces against the Sassanian Empire in a series of battles; and then the death of Julian in 363 in Ctesiphon left the Empire in need of a new emperor.

The frontiers were peopled by ‘barbarians’ who wished to partake in the wealth and dynamism of the Roman Empire. Frontier ‘barbarian’ communities tended to be wealthier, as trade opportunities opened up. Many entered the Empire as mercenary soldiers – foedati. The subsidies paid to them were used to purchase Roman goods, like wine and household materials.[14] There are numerous examples of Roman imperial policy employing ‘barbarians’ in the military campaigns undertaken in the fourth century and earlier. Goths assist Constantine in his battle against Licinius.[15] In the 330’s Constantine instituted close formal ties with the Tervingi on the understanding they would provide military service if called upon.  Barbarian’s commanded Roman forces in the west, the Frank Bauto 380 to 385, Arbogast 388 to 394 and later Stilicho.[16] Intermarriages occurred between the families of these powerful ‘barbarians’ and the emperors.[17] Theodosius I marries his adopted daughter to Stilicho, a half-Vandal.

It was not imperial policy, to make all ‘barbarians’ Roman mercenaries, there were many more instances of Rome’s militaristic aggression toward those who were on their frontier borders. Rome had traditionally combined policies of force and diplomacy when dealing with ‘barbarians’ on its frontiers.[18] Zosimus informs us that Constantius:

 “saw the Roman empire being dismembered by barbarian incursions…”[19]

Ammianus tells us that during the reigns of Valentinian and Valens:

 “the whole Roman world heard the trumpet-call of war, as savage peoples stirred themselves and raided the frontiers nearest to them”.[20]

There were the Alamanni in Gaul and Raetia; Samartians and Quadi in Pannonia; Picts, Saxons, Scots and Attacotti in Britain; Austoriani and Moorish tribes in Africa; Persians in Armenia; and Goths in Thrace and Moesia. In Gaul the Rhine frontier, which had been re-established by Julian, was further reinforced by Valentinian.[21] Ammianus describes the campaign of Caesar Julian in Gaul, fighting the Alamanni and the Franks.[22] Ammianus’ views, although a wonderful contemporary ancient source, must be tempered by their subjective nature, as he was part of the campaigning imperial force.

In 365, the Alamanni invaded Gaul due to a dispute over New Year’s gifts.[23] Symmachus’ panegyrics of 369 extolled the virtue of Valentinian, whose court was located in frontier military camps, as the emperor campaigned in Gaul against the Goths for the greater part of a decade.[24] Humphries highlights the fact that Valentinian issued a coin with a figure, depicting himself, wearing a diadem and “holding a standard and dragging a barbarian captive by the hair” and the message ‘securitas reipublicae’.[25]  This image, according to Mitchell, had become “a visual cliché” to celebrate Rome’s victories.[26] The relationship between the fourth century warrior Roman emperors and the ‘barbarians’ was complex and often involved a mix of deal making and brutal military actions. The popularity of emperors with their subjects often depended on a public relations diet, rich with victories and conquests. At the same time, the need for military conscripts, Foedati, demanded that they paid subsidies in the form of gifts to maintain these forces where they were most needed. Ammianus tells us of Valentinian’s “shrewdness” in checking ‘barbarian’ incursions by maintaining competing tribes as frontier barriers.[27]  This was the case when the Burgundians were enticed by the Emperor to attack the Alamanni on the Rhine border.[28] In 367-369 Valens fought against the Tervingi forces of Athanaric until the Treaty of Noviodunum was signed, which broke the previously close arrangement between the Goths and Rome.[29] Tervingi Goths were allowed entry across the Danube, seeking asylum because of incursions by the Huns, in 376 by Valens; if they converted to Christianity. In 378, at Adrianople, Valens and his army were destroyed by the Gothic forces, after Roman officials enraged the Goths, according to Ammianus.[30] James states that Adrianople was “the greatest defeat” inflicted by ‘barbarians’ since Varus in AD 9.[31]

Our knowledge of the frontier existence is derived, primarily, from archaeological evidence. Wells mentions the economic impact the exchanges between Rome and the scattered communities around the borderlands generated. He identifies the desire for Roman pottery and bronze ornaments as a stimulus for the frontier peoples to produce larger agrarian surpluses to trade with.[32] Runic evidence points to the development of written language, which may have been inspired by contact with Latin.[33] One frontier area, geographically defined by the Danube River and located in modern lower Austria and Czechoslovakia, was recently examined. This region in Roman late antiquity was occupied by two Germanic tribes, the Marcomanni and the Quadi.[34] Pitts states that there were brief periods of hostility between Roman forces and the Suebians, but that it was “diplomacy rather than military strength” which kept the peace along this frontier.[35]  Archaeological evidence suggests that a strong economic relationship did exist, with numerous Roman artefacts found; including coins.[36] A coin showing Antoninus Pius celebrating the appointment of a new Quadi king is very revealing; interestingly the image depicts them as equals in terms of image size. Pitts does not interpret the relationship as that of a client king.[37]

Around 340 the Arian Gothic bishop Ulfilas translated the Christian bible into the Gothic language; using the uncial Greek alphabet.[38] There are no other extant literary remains in the Gothic language than parts of the bible; which makes finding a ‘barbarian’ viewpoint difficult on any issue. Their Arianism is due to the influence of Constantine, who was similarly inclined, and his administration promulgated Christianity as the official religion of the Roman Empire.[39] Christianity must be seen as a major cultural transference from Rome to the ‘barbarian’ peoples in Europe, along with Roman law.

Whittaker determined that one million barbarians crossed illegally into the Roman west during the fourth century and coined the term ‘osmosis-hypothesis’ to describe a possible determinate for the eventual western Roman Empires decline into ‘barbarian’ kingdoms. Drinkwater, however, points out that the ‘osmosis-hypothesis’ is “dependant on specific interpretations of archaeological data”, which in his view cannot sustain the argument.[40]

In conclusion and as shown, the Roman system of frontiers and ‘barbarian policy’ in the fourth century was a complex mix of military, political, economic and social interaction between peoples who classified themselves as Roman and those who lived on the borders and were considered non-Roman; and thus ‘barbarians’. Emperors and their imperial forces had a highly pragmatic relationship with the ‘barbarian’ peoples on their borders. Militarily, they used them to defend their territory when it was convenient to their purposes, as mercenaries, and sometimes as buffers to other competing tribes. Politically, ‘barbarian’ elites and their soldiers were coopted into the civil wars on various sides of competing emperors during the fourth century. Economically, the peoples on Rome’s borders benefitted from contact with the Empire, through trade, subsidies and raiding. Culturally, Christianity, Roman law and written language have permeated beyond the frontiers and embedded themselves within the ‘barbarian’ civilisations; which in the west superseded the Roman Empire. The frontiers and ‘barbarian policy’ were important to Romans because, in many ways, they defined the Empire and what it meant to be Roman.

 ©Robert Hamilton


Ammianus. “Res Gestae.” In The Later Roman Empire. Hammondsworth: Penguin, 1986.

Borst, Arno. Medieval Worlds: Barbarians, Heretics and Artists in the Middle Ages. Translated by Eric Hansen. Cambridge: Polity Press, 1996.

Drinkwater, J.F. “The Germanic Threat on the Rhine Frontier: A Roman-Gallic Artefact?” In Shifting Frontiers in Late Antiquity edited by R.W. Matheson. Aldershot: Variorum, 1996.

Goffart, W. “Rome’s Final Conquest:The Barbarians.” History Compass 6,  (2008): pp 1-29.

Humphries, Mark. Nec Metu Nec Adulandi Foeditate Constricta: The Image of Valentinain I from Symmachus to Ammianus. Vol. 10 Late Roman World and Its Historian: Interpreting Ammianus Marcellinus, Edited by Jan Wilhelm Drijvers. London: Routledge, 1999.

James, Edward. Europe’s Barbarians, Ad 200-600. New York: Routledge, 2009.

Jones, A. H. M. “The Date and Value of the Verona List.” Journal of Roman Studies 44,  (1954): pp 21-29.

Julian. “Oration 1.” In The Works of the Emperor Julian, 1: Loeb Classical Library.

Mann, J. C. “Power, Force and the Frontiers of Empire.” Journal of Roman Studies 69,  (1979): pp 175-183.

Millar, Fergus. “Emperors, Frontiers and Foreign Relations, 31 Bc to Ad 378.” Britannia: A Journal of Romano-British and Kindred Studies 13,  (1982): pp 1-23.

Mitchell, S. A History of the Late Roman Empire 2nd ed. Malden MA: Blackwell, 2015.

Pitts, Lynn F. “Relations between Rome and the German ‘Kings’ on the Middle Danube in the First to Fourth Centuries Ad.” Journal of Roman Studies 79,  (1989): pp 45-58.

Seager, Robin. “Roman Policy on the Rhine and the Danube in Ammianus.” The Classical Quarterly 49, no. 2 (1999): pp 579-605.

Southern, Pat. Late Roman Army. Vol. 3. New Haven: Yale University Press, 1996.

Sowerby, Robin. Companion to the Gothic. Oxford: Blackwell Publishers, 2000.

Wells, Peter. The Barbarians Speak: How the Conquered Peoples Shaped Roamn Europe. Princeton N J: Princeton University Press, 1999.

Whittaker, C. “Limes.” In Late Antiquity: A Guide to the Postclassical World, edited by G. W. Bowerstock, pp 542-543. Cambridge: Belknap Press of Harvard University Press, 1999.

Whittaker, C. R. Frontiers of the Roman Empire: A Social and Economic Study. Vol. 5. Baltimore: John Hopkins University Press, 1994.

Wolfram, Herwig. History of the Goths. Berkeley Los Angeles: University of California Press, 1990.

Zosimus. “New History.” In New History: A Translation with Commentary, 3. Sydney, 1982.

[1] Arno Borst, Medieval Worlds: Barbarians, Heretics and Artists in the Middle Ages, trans., Eric Hansen (Cambridge: Polity Press, 1996). p

[2] C. Whittaker, “Limes,” in Late Antiquity: A Guide to the Postclassical World, ed. G. W. Bowerstock(Cambridge: Belknap Press of Harvard University Press, 1999).

[3] C. R. Whittaker, Frontiers of the Roman Empire: A Social and Economic Study, vol. 5 (Baltimore: John Hopkins University Press, 1994). p 133

[4] J. C. Mann, “Power, Force and the Frontiers of Empire,” Journal of Roman Studies 69, (1979). p 180

[5] Whittaker. p 135

[6] S. Mitchell, A History of the Late Roman Empire 2nd ed. (Malden MA: Blackwell, 2015). p 94

[7] W. Goffart, “Rome’s Final Conquest:The Barbarians,” History Compass 6, (2008). p 6

[8] Pat Southern, Late Roman Army, vol. 3 (New Haven: Yale University Press, 1996). p 39

[9] Robin Seager, “Roman Policy on the Rhine and the Danube in Ammianus,” The Classical Quarterly 49, no. 2 (1999). p 579

[10] A. H. M. Jones, “The Date and Value of the Verona List,” Journal of Roman Studies 44, (1954).p 21

[11] Goffart, “Rome’s Final Conquest:The Barbarians.” p 3

[12] Whittaker. p 134

[13] Julian, “Oration 1,” in The Works of the Emperor Julian (Loeb Classical Library). p 53

[14] Mitchell. p 270

[15] Herwig Wolfram, History of the Goths (Berkeley Los Angeles: University of California Press, 1990). p 60

[16] Mitchell. p 270

[17] Ibid. p 270

[18] Fergus Millar, “Emperors, Frontiers and Foreign Relations, 31 Bc to Ad 378,” Britannia: A Journal of Romano-British and Kindred Studies 13, (1982). p 8

[19] Zosimus, “New History,” in New History: A Translation with Commentary (Sydney: 1982). 3. 1

[20] Ammianus, “Res Gestae,” in The Later Roman Empire (Hammondsworth: Penguin, 1986).  XXVI: 4.3

[21] Mann, “Power, Force and the Frontiers of Empire.” p 181

[22] Ammianus, Res Gestae, XVI: 1

[23] Ammianus, XXVI; 5.7

[24] Mark Humphries, Nec Metu Nec Adulandi Foeditate Constricta: The Image of Valentinain I from Symmachus to Ammianus, ed. Jan Wilhelm Drijvers, Late Roman World and Its Historian: Interpreting Ammianus Marcellinus, vol. 10 (London: Routledge, 1999). p 119

[25]Ibid. p 120

[26] Mitchell. p 269

[27] Ammianus, Res Gestae, XXIX: 4

[28] Ammianus, Res Gestae, XXVIII: 5;9-13

[29] Goffart, “Rome’s Final Conquest:The Barbarians.” p 7

[30] Ammianus XXXI; 6.2, 13.7

[31] Edward James, Europe’s Barbarians, Ad 200-600 (New York: Routledge, 2009). p 52

[32] Peter Wells, The Barbarians Speak: How the Conquered Peoples Shaped Roamn Europe (Princeton N J: Princeton University Press, 1999). p 255

[33] Ibid. p 256

[34] Lynn F. Pitts, “Relations between Rome and the German ‘Kings’ on the Middle Danube in the First to Fourth Centuries Ad,” Journal of Roman Studies 79, (1989). p 45

[35] Ibid. p 46

[36] Ibid. p 54

[37] Ibid. p 49

[38] Robin Sowerby, Companion to the Gothic (Oxford: Blackwell Publishers, 2000). p 18

[39] Ibid. p 18

[40] J.F. Drinkwater, “The Germanic Threat on the Rhine Frontier: A Roman-Gallic Artefact?,” in Shifting Frontiers in Late Antiquity

  1. R.W. Matheson(Aldershot: Variorum, 1996). pp 23-24