Frontier wars and immigration policy in second-century Rome

Military decline and the barbarization of the Empire

The extent of knowledge that Romans in the second century AD had of the Germans across the frontier came largely from Tacitus’ Germania, written sometime after 80 AD at a time when tribal chiefdoms numbered in the tens of thousands. By the time Marcus Aurelius and Lucius Verus were co-emperors, this had changed as loose German confederations – earlier used for defensive wars – had now solidified into nomadic tribal alliances comprising several tribes under the rule of a single king.

The Cherusci, Chatti and Marsi of the earlier wars fought by Tiberius and Germanicus after the Varian disaster were small warbands which could join together in emergencies but only for a short time. These tribes warred more with each other than with the Romans and soon fell apart or became easy prey for more united peoples.

Whereas Tiberius’ policy of forsaking further expansion into Germany may have been the more prudent policy for the empire in the first century AD, a more assertive frontier policy seemed in order for the second century of imperial rule as different Germanic Tribes, now under pressure from encroaching Slavic Peoples, had begun to coalesce into larger groups for defence or face absorption by less civilized tribes heading west. Conversely, they were also beginning to demand assistance from the empire or barring that entrance into it.

Roman frontier policy

Their opportunity came with Rome’s long war in Parthia and subsequent plague which left the Rhine and Danube garrisons depleted. The resulting depopulation of the countryside would have greatly affected Roman agriculture as well as military recruitment and would then signal to Rome’s clients along the Rhine and Danube Rivers an opportunity to reorder the existing political framework which was organized solely around Roman military dominance.

The situation along the frontier was typical in a world without nation states. That is to say that the Empire claimed to rule over barbarian lands across its borders even though it did not have effective control over this territory. It was able to effectively reduce them to the status of clients thereby making sure that “friendly” tribes occupied the territory adjacent the empire’s borders while keeping more aggressive tribes away from the border regions.

Another useful policy was promoting conflict, should it threaten to erupt, among the more warlike tribes farther away who otherwise might prove hostile towards Rome’s clients or the Empire itself. Similar divide and conquer policies have been implemented by great powers throughout the ages and are used still today. In exploiting the natural aggressiveness of their enemies across the northern frontiers the Romans were following a timeworn policy, which had been in place since at least the time of Tiberius after the closing of the frontier in Germany. However policy makers did not take into account the effect it would have on both friendly and hostile tribes alike, namely that of dependency for Rome’s clients on the one hand and experience and hardness among her enemies on the other.

Increasingly fragile borders

As Roman clients came to rely more and more on Roman arms for protection they also experienced increasing pacification, while the more fierce tribes farther out experienced something along the lines of natural selection. The weaker tribes seeking shelter either with Rome, or submitting to or joining the stronger ones. This in effect had made the warlike tribes much bigger and stronger until they were able to form kingdoms where before there were merely chiefdoms or unstable confederations.

Roman weapons also made their way into the hands of tribes dwelling on the outer fringes of Germanic Europe. Roman swords, daggers and even cavalry helmets for example have been found in graves as far away as Denmark and Sweden. There was little the Romans could do to control the situation on the ground though and the results would come back to surprise them during the Marcomannic Wars and would continue to chip away at the frontiers until the final collapse of the empire in the fifth century.

If the Romans could not be expected to greatly influence local politics among the larger and more powerful tribes like the Marcomanni or Quadi they could also not be expected to incorporate them into the empire either as clients or as potential subjects, who would be allowed to enter and settle in the empire due to their general unruliness. Providing the Marcomanni with a king of the Romans’ choosing might have also been problematic given the need for legitimacy. Placing garrisons throughout their territory would have been costly and further strained the empire at a time of serious manpower shortages. Improving defenses along the frontier would only delay the problem as increasing pressure was mounting from Slavic tribes moving west and forcing a decision on the Germanic peoples.

The Marcomannic Wars

The weakening of the imperial armies likely convinced the Marcomanni and Quadi of the need to act while the possibility still remained. In fact the emperor had already begun to turn his attention to the Rhine and Danube frontiers strengthening garrisons and interfering in the internal affairs of friendly tribes as a way of shoring up defenses after the heavy losses to the Parthians. To the Marcomanni and the Quadi this must have seemed like the last straw in a long list of grievances against the Romans. For them the emperor focusing his attention towards the Rhine and Danube frontiers was a closing of the window which would necessitate immediate action.

The action decided on was a pre-emptive war both as a way to thwart the emperor’s own war plans while forcing an opening through the weakened frontier defenses and perhaps to present the Romans with a fait accompli and hold at least some of the conquered territory after any settlement. For years there had been small scale raids carried out for the purpose of looting, first by the Chatti and Chauci and later by the Langobardi moving in force. And with the long years of peace under Antoninus Pius softening the empire and its armies it was not so difficult for larger forces to push through weakened defenses.

This all had the effect of making the initial incursions go undetected as the vanguard of an invasion force headed straight into the Mediterranean heartland of the Roman state. Defensive measures fell to the local governor of Pannonia as the nearest commander with military forces large enough in the area to deal with the onrush of Germanic and Sarmatian warriors. Marcus Aurelius and his co-emperor Lucius Verus headed for the front as the Marcomanni pushed through northern Italy and laid siege to the city of Aquileia.

After the siege had been abandoned they would set up their headquarters and continue working on plans for pushing the Germans back out of Italy and then for the inevitable counterattack. The war continued on and off for over a decade with both emperors dying during the long struggle with the Germanic tribes. After this, Commodus chose a policy of appeasement while relying on natural borders and even though the front would stabilize the problem of secure borders would continue to perplex strategists and military planners right into the next century.

Securing the northern borders

The problem of secure borders in the north would repeatedly insert itself into the political life of the empire over the next two centuries. Strategically minded emperors like Tiberius and Marcus Aurelius might have prolonged the life of the empire. The chaos and losses of the Parthian and Marcomannic Wars and their aftermath, such as the succession of Commodus and the deserter’s war which raged for a time in Gaul, were signs that the empire was indeed weakening under the constant strain of having to deal with wars in the east and the beginnings of the Völkerwanderung across the northern frontier.

Over the next century, the empire would be plagued with border incursions leading to economic and military strain and to civil war imposing one short lived and bankrupt regime after the next. If the Roman world had been more stable, it could have found the necessary time and energy to strengthen its borders while instituting a more workable frontier policy. The Romans could have made the strategic retreat to more defensible lines along the Rhine and Danube Rivers less problematic while treating the Dacians, Marcomanni and Quadi as clients with small garrisons dispersed throughout their territories helping these peoples to resist the more aggressive Slavic tribes.

As it was, these territories and their garrisons, which included the Agri Decumates and Dacia, were abandoned. Without the presence of garrisons in their territories, these emergent peoples – many of them fully Roman to an extent that Western colonizers could not claim of their own native peoples in the nineteenth and early twentieth centuries – were doomed to fall back into barbarism or be forced to submit to less civilized tribes invading their territories.

The collapse of the colonial empires in the twentieth century saw similar parallels with constant war and hostile regimes replacing the imperial administration which had hastily left the scene. So it was for the Romans, who were witnessing the collapse of their once great state, and for the provincials who were abandoned by them and then left to fend for themselves in an increasingly hostile world.

Travis Chittom studied Anthropology at Broward College. He then worked in the airline industry for Northwest Airlines, before enlisting with the US Army in 2006, where he served with the Second Stryker Cavalry Regiment in central Iraq (Taji) and in Diyala Governate. He currently lives in Bad Homburg Germany with his wife Tina and is working on a book about Sargon the Great.

Further reading

  • Adrian Goldsworthy, How Rome Fell: Death of a Superpower (New Haven & London 2009).
  • Peter Heather, Empires and Barbarians: Migration, Development and the Birth of Europe(London 2009).
  • Theodor Mommsen and Thomas Wiedermann (eds.), A History of Rome under the Emperors(London & New York 1996).
  • Xenia Pauli Jensen, “Preliminary Remarks on Roman Military Equipment from the War Booty Sacrifice of Vimose, Denmark”, Roma: L’Erma di Bretschnider (2007), pp. 131–136.
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