The Roman empire stretched on one diagonal from Hadrian's Wall to northern Iraq, and, on the other, from the mouth of the Rhine to the Atlas mountains of north Africa. It was the largest state that western Eurasia has ever seen: larger, for instance, than even the enlarged European Union, and certainly dwarfed the largest of Europe's medieval empires. It was also extremely long-lived. Transylvania and Britain apart, where it lasted only one hundred and seventy years and three hundred and fifty years respectively, Roman rule prevailed over the remainder of its domains for an astonishing five hundred years. And all this in a period where the speed of bureaucratic functioning and of military response rattled along at 45 kilometres a day, something like one tenth of modern counterparts. Measured in terms of how long it took real people to get places, the Roman empire was arguably ten times as big, even, than it appears on the map.
The epic scale of its existence has always sharpened interest in the causes of collapse. And, since Gibbon, while a role has always been allocated to outside invasion, explanation has tended to focus on a range of internal transformations and problems as the prime movers in the processes of Roman imperial collapse which brought the western half of it to an end in the fifth century AD. Gibbon famously drew attention to the empire's top-heavy 'stupendous fabric', and to the supposedly problematic effects of Christianisation, while, by the mid-twentieth century, attention commonly concentrated upon the economic collapse and political chaos which were seen as typical of the later Roman empire of the fourth century.
The entire vision of late-Roman economic collapse was based, however, on a limited body of evidence: assorted literary references to hyper-inflation in the third century and various problems associated with the raising of taxation from the agricultural economy in the fourth; and the brute fact that the per annum level of inscriptions commissioned for display, usually in urban contexts, suddenly dropped to about one-sixth of former levels in the middle of the third century. From this it was generally concluded that there was a 'third-century crisis', destining the empire for collapse, with a number of key components. Agriculture, first of all, the main engine of Roman economic production, was held to be misfiring badly; the commonest view was that over-taxation was not leaving the peasantry with sufficient food, generating a slow but significant decline in population and output. If the peasants were in trouble at one end, then the hyper-inflation and end of inscriptions reflected the economic plight of the upper, land-owning classes, who were increasingly operating on a shoe-string, and, as a result, had no stomach for the public service which the inscriptions had often celebrated. Indeed there is much fourth-century legislation designed to force the land-owning classes to fulfill the kind of local-governmental functions for which they had previously competed. The empire's top-level political structures, equally, were in similar disarray, with the mid-third century seeing so many short-lived emperors, often vying for power simultaneously, that we still do not know exactly how many contenders for power there were. No wonder outside invasion was thought to be pushing against a structure ready to collapse.
In the last thirty years, however, this consensus has been entirely overturned by an archaeologically-driven revolution. It was presaged by a unique find of the 1950s. Operating in the limestone hills outside Antioch, ancient capital of the Roman east, a French archaeologist called Gustav Tchalenko came across stone-built villages of the late-Roman period, abandoned and never reoccupied around 800 AD, which showed every sign of prosperity in the fourth century and afterwards. Most late-Roman peasants built in much less durable materials, so that this kind of fossil Roman landscape was impossible to find elsewhere and its broader significance impossible to estimate. Even so, the more astute were already realizing that scholarship would have to reckon with a more prosperous late-Roman economy than had been supposed.
Confirmation of the point had to wait until the 1970s, when archaeologists developed, for the first time, a method for sampling general levels of rural productivity. This relied on the fact that modern ploughing bites deep into long-submerged stratigraphic layers, bringing to the surface much ancient pottery. Long-term regional survey projects spent the summers collecting every fragment in the target zones, and the winters analyzing the results. Since many Roman pottery sequences are so well-known that many pots can be dated to within ten to twenty years, and since soundings and excavations had established the kinds of densities of pottery that were likely to reflect the existence of a settlement, two things became possible. Comparisons of pottery densities made it possible to estimate the number of Roman settlements in any region. The dating structures of those assemblages then made it possible to show precisely when, within the 500-year Roman era, any particular settlement had been occupied.
The work was long and hard, but the results revolutionary. Against all expectation, and small areas of northern Britain and north-eastern Gaul apart, the fourth century has emerged as the period of maximum agricultural activity, measured in numbers of settlements, within the entire Roman period, and not the minimum as the old paradigms had supposed. A large rural population might mean, of course, poorer individual peasants, as it did in medieval England before the Black Death, and says nothing about the levels of taxation under which they laboured. Nonetheless, total rural output, and hence total GIP - gross imperial product - was clearly higher in the late-Roman period, than ever before. As a result, it is no longer possible to explain fifth-century political crisis in terms of preceding economic collapse.
None of this eradicates the third-century crisis, but it has imposed limits on its importance. It neither generated nor was prompted by a general crisis in agricultural production. Nor was the hyper-inflation of the same ilk that destroyed middle-class savings and generated such political unrest in Germany after the First World War. Third-century Roman inflation was limited to prices measured in silver coins, and reflected the fact that the amount of silver they contained fell into drastic decline. Gentry wealth in the Roman world came in the forms of land and its output, and treasures in gold and purer silver, none of which lost its value. What the hyper-inflation was all about, in fact, was minting enough coins to pay an army which was increasing in size out of all proportion to the stock of silver available. And this, straightforwardly, was the product of exogenous shock. From the 230s onwards, the Sassanian dynasty reorganized a huge region of west Asia - Iraq and Iran in modern terms - to create a superpower rival to the Roman empire. This new power announced itself with three massive victories over different Roman emperors, the last of whom, Valerian, was captured, led in chains, and then skinned and tanned after his death. The Persian threat was eventually countered by the end of the third century, but it took fifty years or so of military and fiscal adjustment to mobilize the necessary resources.
If less directly, the rise of Persia also played a major role in the political dislocation of the third century, both centrally and in the localities. Centrally, the new Persian threat meant that emperors were being dragged more or less permanently towards the east. This left a power vacuum in the west, and many of the usurpations of the period were really about filling that gap. Overall, the rise of Persia made it pretty much inevitable that the late Roman empire would have to operate with more than one emperor at a time. It had only been avoided previously, despite the empire's size, by the fact that its enemies were relatively unthreatening.
The massive decline in inscriptions has some broader roots but was also linked to the rising Persian star. The whole point of the participation in public life recorded by the inscriptions was to compete for power within the main organ of local government: the town councils which each ran a dependent rural territory. In the early-imperial period, the councils controlled substantial funds, which is why local gentry and bigger fish maneuvered to win power upon them, with the urgent self-publicity recorded in the inscriptions. The central Roman state had long been helping itself to these funds, but the Persian crisis saw their final confiscation. With that act, the whole point of local politics was removed, and local service became much less attractive. Instead, local landowners moved increasingly into imperial service in the late-third and fourth centuries, where all the good perks were to be had, as central bureaucratic structures expanded to control the new fiscal structures paying for the larger army. Quickly, however, bureaucratic expansion also became a political tool, and by the mid-fourth century emperors were often granting honorary bureaucratic status to individuals who had never wielded a quill in their lives.
Again, therefore, the extent of crisis has had to be re-evaluated. The large imperial bureaucracy of the fourth century used to be one of the bogeymen of the 'decline and fall' story: a parasitic body of 'idle mouths' which sucked the life out of the poor taxpayers. When it is realized that most of its members were the old local Roman gentries in new guise - who had previously been equally 'idle' on their town councils, then it is much less clear that their appearance in the fourth century presaged fifth-century collapse. That is not to say that everything in the garden was rosy. The Persian threat had been parried not eliminated, so that resources had to be pointed eastwards still. Dividing imperial authority generated friction and periodic civil war even between brothers sharing the throne, while economic output was not easy to increase in the absence of tractors or artificial fertilizers. Overall, however, this more moderate level of third-century crisis makes vastly more sense of the overwhelming evidence for fourth-century cultural vitality, the era in which Christianity was, almost without effort, made part of the classical world by a host of inventive accommodations. It also makes more sense of the brute fact that, even after the fall of the west in the fifth century, the eastern half of the empire - operating with the same institutions - carried on successfully for centuries. Finally, it poses Gibbon's question with renewed vigour: if there is no sign of major dislocation within the late-Roman imperial system of the fourth century, why did its western half cease to exist in the fifth?
A second intellectual revolution, again largely driven by archaeological investigation, suggests an alternative line of thought to traditional paradigms of internal collapse. For those with eyes to see, clues were already there in the limited stock of historical evidence available for non-Roman Europe. Early in the third century, the traditional cast of small groupings which confronted Roman power across the frontier in the early imperial period, most but not all of them Germanic speakers, was replaced by a smaller number of larger entities. This refashioning prevailed all along Rome's European frontiers, from the new Frankish coalition at the mouth of the Rhine, to the northern Black Sea littoral where Goths emerged as the new power in the land. The full significance of these changes in nomenclature was far from clear, however, since some of the new entities certainly represented fresh coalitions of pre-existing social units.
As a large body of archaeological evidence has now shown, however, much more was afoot beyond Rome's frontiers than mere changes of name. In the course of the Roman period - broadly the first four centuries AD - central and northern Europe saw its own economic revolution. Most fundamentally, there was a massive increase in agricultural production, fuelled by an intensification of farming regimes. This shows up in the range of crops being grown, the tools used, and a steady increase in both size and density of settlements. Levels of trade and exchange also increased markedly, with some evidence for more specialized production. There are also unmistakable signs of increasing differentials in wealth and status between different sections of society, with an ever greater prominence being assumed by a militarized segment of the male population. Indeed, all the various new terms for 'authority' which came into use among different Germanic-speaking populations in the Roman period evolved from words which had the basic meaning of 'war-leader'. Between the birth of Christ and 400 AD, the non-Roman population of Germanic Europe both increased substantially in wealth and size, and also threw up new structures of authority and social power. It was these transformations which underlay the appearance of the new named groupings on the other side of Rome's European frontiers.
These new political structures proved much more formidable than those they replaced, and this already shows up in third-century events. The real origins of this crisis certainly lay in Persia, but it also had a strong western component. The new coalitions of 'barbarian' Europe not only raided widely across Roman territory as emperors struggled to deal with the Persian threat, but even forced the empire to abandon certain of its territories: a salient in what is now southern Germany between the Rhine and Danube, and Dacia in what is now Transylvania. These were arguably strategic withdrawals, not headlong retreats, but, for the first time, firmly-ruled Roman territory had passed out of imperial control. And, in the fourth century, these new frontier groupings operated as only semi-subdued clients of the empire. They did contribute to imperial armies on occasion, but also required regular Roman military campaigning and targeted foreign aid to willing kings to keep them in line. The imbalance of power in favour of the Mediterranean, which had allowed the Roman empire to come into existence, was being eroded by Persia, and also by the rise of new structures in non-Roman Europe.
Less obvious, while some of these processes of transformation had longer-term roots, the projection of Roman imperial power had hugely increased their scope and speed of impact. The Sassanian dynasty united west Asia, for instance, taking over from the previously dominant Arsacids, on a straightforwardly anti-Roman ticket. The prestige and wealth which came to it from its successful wars against a succession of Roman emperors was the cornerstone of its new authority.
Likewise in Europe, a whole series of different interactions with the Roman world generated or at least speeded up the crucial transformations which turned Rome's neighbours into much more formidable adversaries. For one thing, the Roman empire stationed large numbers of troops right on its Rhine and Danube frontier lines. At least some of the agricultural expansion beyond these frontiers profitably serviced the huge demand for foodstuffs, leather and so forth that this unprecedented concentration of man- and spending-power represented. Roman demand for luxury items, notably amber and slaves, also stimulated development across the frontier and brought new wealth into the Germanic world. The same was true of Roman diplomatic subsidies, which, in the form of annual gifts, represented a regular flow of new wealth across the frontier from the earliest period. And alongside this, of course, was all the wealth resulting from raids mounted upon the frontier groups' rich Roman neighbours: cross-border raiding being entirely endemic.
All this new wealth then came to underpin the new social and political hierarchies as fierce struggles were let loose in the non-Roman world to control its various sources and flows. As the new words for authority indicate, the evidence is that these struggles were military and direct. Not least, the new wealth flowing across the frontier was quite unequal in its geographical distribution, with diplomatic subsidies and both raiding and trading opportunities falling most naturally to those nearest the frontier. The wealth of the frontier region, however, quickly became a target for those less-fortunate groups set further away. One marked pattern of adjustment in the second and third centuries, therefore, saw groups from beyond the immediate frontier zone organize and arm themselves to seize a corner of the action from those previously monopolizing it. This was the basic motivation behind the arrival of Goths on Rome's Danubian frontiers in the third century, and played some part too in the reorganizations in the west. These expansions were naturally carried forward by military action, since the group already profiting from its position near the frontier was not about to give up its advantages voluntarily. Roman aggression itself even carried the process forward by another route. From the first decade of the first century AD, one consistently-documented motive for banding together in larger groups was the desire to resist more effectively the worst intrusions of Roman domination.
Many contingent sequences of events contributed to the fall of the western half of the Roman Empire. Not least, the sudden explosion of Hunnic power out of the Eurasian steppe and into the eastern fringes of Europe generated two major pulses of migration into the Roman world, one 376-80, the other 405-8. By 440, their component parts had coalesced into two major alliances, each much larger than any of the groups which had existed beyond the frontier: the Visigoths in southern Gaul and the Vandals in north Africa both representing amalgamations of three separate immigrant groups of 10,000 plus warriors. The immigrants had in the process inflicted great damage on the west-Roman state structures by first mincing their armies and then preventing their proper replacement by either ravaging or annexing key areas of their tax base. This in turn allowed Anglo-Saxons and Franks to take over former Roman territories in Britain and north-eastern Gaul, weakening state structures still further. The immigrants also acted as alternative sources of political magnetism for local Roman elites. Given that these elites were all landowners, and could not therefore move their assets to more desirable locales, they were often faced with little choice but to come to agreements with immigrants as they became locally dominant: if, that is, the immigrants were willing to do so. In this way, the west-Roman state eventually faded away, if not without vigorous martial efforts to restore its fortunes, sometimes made with substantial aid from the Roman east, as revenues fell away to the point where it could no longer put effective forces in the field against the immigrants who were busy expanding their zones of control.
In all this, the entirely contingent impact of the Huns is clear. Without it, the two main pulses of migration, each involving several major groups, would never have occurred in short enough order to prevent the Roman authorities from dealing with the migrants which, had each group arrived separately, they certainly could have managed. The effect of the internal limitations of the Roman state is also clear, not least in its inability to increase revenues markedly beyond fourth-century levels as the new crisis began to bite after 400. The ability of the immigrants to detach Roman landowners politically from their allegiance also reflects the naturally loose levels of control exercised locally by such a geographically vast state encumbered with such primitive modes of communication. And, of course, the eastern half of the empire was always able to pick and choose the moments and scale of its assistance to the west, where a single united imperial authority might have been willing to take greater risks.
But even giving these points due weight, the external factor - represented by the immigrants of 376-80 and 405-8 - was the prime mover behind western-imperial collapse. The empire's internal limitations only came into play because the immigrants put pressure on its structures, and there is no sign that, by themselves, these limitations would have brought the it down, any more than they had done over the preceding half millennium. Two further considerations underline the point. First, the eastern half of the empire carried on happily enough for more than another century using precisely the same structures. Second, the main limit upon the empire's ability to respond to crisis in the fifth century - the lack of any further slack in its fiscal/military systems - had in any case been caused by another outside factor: the rise of Persia in the third century.
The more contingent aspects of the crisis could not have had the same cumulative effect without the transformations generated in non-Roman Europe by centuries of interaction with its imperial neighbour. Had the Huns arrived in the first or second century, the kind of Germanic group that might have been set on the march would not have been large or coherent enough to survive its initial brush with Roman power. Germanic groups of this period could field no more than a few thousand warriors at most. By the same token, the processes of political amalgamation required to generate warrior groupings of a few tens of thousands, on the scale of the fifth-century Visigoths or Vandals, would have been so complex, involving so many small separate parts, that they are highly unlikely to have been completed successfully before the individual groups were destroyed by a Roman empire, which prior to the rise of Persia, still had plenty of fiscal/military slack in its systems. There is a strong sense, therefore, in which imperial Roman power and wealth created - over the long term - its own nemesis, by generating opposing forces which were powerful enough to match its military might. And here, if nowhere else, the fall of the western Roman empire might still have lessons which modern empires would do well to ponder.
P.R.L. Brown, The World of Late Antiquity: AD 150 - 750 (London, 2004).
J.F. Matthews, Western Aristocracies and Imperial Court AD 364-425 (Oxford, 1975).
B. Ward Perkins, The Fall of Rome and the End of Civilisation (Oxford, 2005).
C. Wickham, Framing the Early Middle Ages: Europe and the Mediterranean 400-800 (Oxford, 2005).
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