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Innovation and Stagnation: Military Infrastructure and the Shifting Balance of Power between Rome and Persia
Eberhard W. Sauer, Jebrael Nokandeh, Konstantin Pitskhelauri and Hamid Omrani Rekavandi
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Abstract
The Roman Empire, and its eastern and western successor states, controlled the majority of
Europe’s population for approximately half a millennium
 (first century BC to fifth century AD), holding dominant power status from the second century BC to the seventh century AD, longer than any other state in the western world in history, and it was also the only empire ever to rule over the entire Mediterranean. Its ability to integrate ethnic groups and its well-organised military apparatus were instrumental to this success. From the third century onwards, however, the balance increasingly shifted, and the physical dimensions of fortresses and unit sizes tended to decrease markedly in the Roman world, and the tradition of constructing marching camps and training facilities seems to have been abandoned. By contrast, the Sasanian Empire increasingly became the motor of innovation. Already in the third century it
matched Rome’s abilities to launch offensive operations, conduct siege warfare and produce
military hardware and armour. Jointly with the Iberians and Albanians, the empire also made skilful use of natural barriers to protect its frontiers, notably by blocking the few viable routes across the Caucasus. By the fifth/ sixth century, it pioneered heavily fortified large rectangular campaign bases, of much greater size than any military compounds in the late Roman world. These military tent cities, filled with rectangular enclosures in neat rows, are suggestive of a strong and well-disciplined army. Like these campaign bases, the contemporary c. 200km-long
 
2 Gorgan Wall, protected by a string of barracks forts and of distinctly independent design, is not copied from prototypes elsewhere either. The evidence emerging from recent joint projects between the Iranian Cultural Heritage, Handcraft and Tourism Organisation and the Universities of Edinburgh, Tbilisi and Durham suggests that in Late Antiquity the Sasanian army had gone in the lead in terms of organisational abilities, innovation and effective use of its resources.
Eight centuries of great power status
 – 
 seven centuries of rivalry
Some 1,400 years ago, in AD 614/615 and again in AD 626, Sasanian armies had reached the Bosporus. They stood opposite what was at the time by far the richest and most populous city in Europe: Constantinople, the capital of the Roman Empire.
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 The Roman Empire had dominated Europe and the Mediterranean, militarily and economically, for almost 800 years, vastly longer than any other state in world history. In the early seventh century, the Sasanian army pus
hed the western world’s most enduring mega
-empire to the brink of annihilation. The Sasanian Empire in the late AD 610s, and for much of the 620s, stretched from Egypt and Syria to the west of the Indian Subcontinent and from the Caucasus and southern margins of the steppes of Eurasia to Yemen (Fig. 11.1). Not just in terms of territorial extent, but also in terms of duration of dominance, the Sasanian Empire was arguably an equal rival to Rome. Whilst lasting for over four centuries, longer than most other political entities of comparable size, this timespan can be doubled, if we bear in mind that it was not a new empire established from scratch in the third century. Instead, the Sasanian Empire should be considered a successor of the Parthian Empire onto which a new dynasty had been imposed via internal revolt (rather than conquest by an external foe). So it is logical to think of just one, Partho-Sasanian, Empire
 – 
 which was the major military and economic power in the Near East for
 
3 roughly the same period of time as the Roman Empire had been in the west, from the second century BC to the seventh century AD. The Sasanian Empire, with its centre of dynastic power being in south-western Persia, differed no more from the Parthian Empire with its northern Persian core, than the early Roman Empire, where Italians held the reins of political and military power up to the first century AD, differed from the high to late Roman Empire, when most of the army and the emperors themselves were recruited from within the frontier provinces. Needless to stress that during the eight centuries or so when the Roman and Partho-Sasanian Empires enjoyed great power status, both underwent numerous fundamental changes; indeed, that they were adaptable to the challenges of the time explains their longevity. Gradual bestowal of citizenship to conquered peoples and the shift of power from conqueror to conquered within the Roman Empire much reduced the risk of rebellion and contributed as
much to the empire’s stability and longevity as t
he efficacy of its armed forces. The late Roman Empire may have had little in common with the second-century BC Republic
 – 
 and the late Sasanian state, little in common with the Parthian Empire centuries earlier
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 except that they had never been completed defeated and subdued by an external force and remained the most dominant political entities in the West and Near East respectively for some three quarters of a
millennium. For seven centuries they confronted each other, from Pompey’s conquest of Syria
in 6
4BC, soon followed by the annihilation of Crassus’ army at Carrhae in 53BC, to the Arab
conquest of Roman and Sasanian possessions in the Near East in the AD 630s. Only two other pre-medieval empires in south-west Asia and the Mediterranean had reached similar geographic size and neither was as long-lasting as the Roman and Partho-Sasanian Empires had been: the Achaemenid Empire, retaining its vast dominion for over two centuries, and
Alexander’s short
-lived realm thereafter.
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 Whilst the Parthian and Sasanian eras should be seen as two phases in the history of one empire, there is no attempt here to downplay the changes the Sasanian dynasty brought about.
 
4 Notably in terms of military capabilities, the Sasanian era saw a series of major innovations, spread over centuries. It is also the Sasanian era, for which we have significant new evidence, and the focus of this paper is thus on this period.
Fashionable relativism and persistent Eurocentrism
The Sasanian Empire’s territorial extent and further expansion in the later sixth and early
seventh centuries, well beyond what had been controlled by the Parthian kings, is a remarkable phenomenon. It is astonishing that some believe nonetheless that the Sasanian army had been disorganised, largely or exclusively non-professional, and that successful defence of an empire of such extraordinary size depended on haphazard arrangements, indeed that there had been no standing army at all for the first three cen
turies of the Sasanian Empire’s existence.
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 Major monuments in the east, such as the Gorgan Wall, are often assumed by default to be imitations of prototypes from the west
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 – 
 sometimes probably a result of subconscious Eurocentrism, not a conscious ideology but a bias towards what we know best. Similarly, if our (mainly western or much later) written sources provide little evidence for permanent Sasanian frontier troops, it is all too easily assumed that there were none. Lack of firm archaeological proof for a well-organised standing army until recently seemingly corroborated this belief. As was perhaps to be expected, this was in part a result of little, if any, fieldwork and state-of-the-art dating techniques at relevant sites, and the picture has radically changed in the twenty-first century. Whilst often underestimating Sasanian capabilities, recent scholarship has frequently overrated those of the late Roman state and
questioned the ‘decline’ of the Roman Empire,
preferring the politically correct term o
f ‘transformation’.
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 Alexander Sarantis argued recently
that the late Roman army ‘performed exceptionally well’, just faced stronger opponents than
before.
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 Such an assessment, even if persuasive, would at least suggest that it had not kept up
 
5 with developments of the time. Yet the evidence paints a rather different picture. Far from being as strong as it had been before, it suggests a marked decline in capabilities. Whilst in the early and high Empire legionary fortresses reached an average size of 20-25ha, housing some 5,000-6,000 soldiers each, in Late Antiquity they tend to be 4-5ha large, perhaps housing a fifth of the garrison. Not only had the legions massively shrunk in size, there no longer were compounds even approaching the size that was widespread up to the third century. There is far less evidence for late antique military barracks than for those of the first three centuries of the Christian era. Whilst written sources
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 postulate that the Roman army had increased in numbers in Late Antiquity, this, if true, will apply to urban garrisons, which are hard to trace archaeologically, not to mention the
 foederati
. The number of troops in permanent military compounds appears to have shrunk massively and those that remained relied on much more heavily def 
ended compounds than Rome’s soldiers had needed before.
 Training similarly appears to have declined. We are not aware of a single training ground, practice camp or new marching camp that is certain to be late antique. Whilst admittedly, none of these installations are easy to date, and whilst there are very few training grounds in total, the complete absence of firm proof for any late antique installations of this kind is significant.
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 Even if there is still the odd reference to late antique camps in the
sources, e.g. during Julian’s
invasion of Sasanian Mesopotamia in AD 363, defences (if any) were basic, consisting of wooden stakes or shields whilst ditches and ramparts or walls appear to have been exceptional.
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 Vegetius, lamenting that soldiers in his time no longer were involved in regular training or built marching camps, to keep them safe from surprise attacks,
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 will not have been far off the truth.
 
The post-war generations, mostly fortunate enough never to have personally experienced war and never confronted with the reality and logic of warfare, have often dismissed the loss of capabilities of the late Roman army or doubted the effectiveness of major military
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