The great cities of the Roman world are among the world’s most iconic archaeological sites. They are also among the most visited places on earth, and as such are evocative reminders of one of the greatest civilisations of the past. This civilisation, the Roman Empire, was enclosed by over 5,000km of frontiers. These are as much a reminder of the empire as its cities. And they have their own iconic sites – Housesteads on Hadrian’s Wall, the Saalburg and Eining in Germany, Aquincum in Hungary, Porolissum in Romania, Qasr Bsher in Jordan, or Lambaesis in Algeria. These sites recall the power and splendour of a fallen empire.
Roman frontiers have been studied by antiquarians since the 15th and 16th centuries. The 18th century witnessed a flourishing of literature about Roman frontiers right across Europe. The 19th century saw the development of a new method of investigation in the form of excavation. At first, this was merely clearance work, but the newly-discovered artefacts needed a home, and thus museums sprang up along the former frontiers, such as Budapest in 1802, Leiden in 1818, Bonn in 1820, Cluj in 1859, and Vienna in 1881.
The 1890s witnessed a major change. Across Europe began the era of scientific excavation. Stratigraphy was recorded, pottery and artefact studies developed, and objects were carefully displayed in the new museums. This decade even witnessed the earliest reconstructions, most notably that of the fort at the Saalburg, where work was undertaken on the instructions of the Kaiser Wilhelm II.
The later 19th century also saw the first stirrings of international discussion and co-operation. Great international projects were established. These included the start, in 1853, of the publication of all known Roman inscriptions in the Corpus Inscriptionum Latinarum. But usually research took different forms within each country.
In Britain, the emphasis was on synthesis. The first modern study of Hadrian’s Wall was published in 1851: John Collingwood Bruce’s Hadrian’s Wall (its successor was last re-edited and re-published in 2006). In Germany, on the other hand, a campaign of survey and excavation followed the establishment of the Reichs-Limeskommission in 1892. The first volume was published in 1894 and the series continued until 1937, when the whole frontier had been faithfully recorded. A commission for the study of the Roman limes in Upper and Lower Austria was formed in 1897.
Romans and barbarians
Roman frontiers have a considerable contribution to make to the study of the Roman Empire. Here, uniquely, Romans met their ‘barbarian’ neighbours on a day-to-day basis. They are the boundary lines through which Roman objects spread outwards from the imperial heartlands across Europe, North Africa, and parts of Asia, reaching as far as India, China, and Korea.
Decades of survey, excavation, and study of the resulting material have created a great body of evidence to help us understand the frontiers. Part of the fun of studying them is having to tackle the fraught relationship between new archaeological evidence and long-known literary sources. And then there are sources that bridge the divide – notably the remarkable discovery of writing tablets at Vindolanda near Hadrian’s Wall: written sources that speak to us of daily life on the frontiers rather than of historical events.
The frontiers of Rome are a product of the empire. The Roman Republic had no need for frontiers, for it was an ever-expanding state. In the last 50 years of the Republic, Pompey campaigned through the Middle East, while Caesar conquered Gaul and invaded Britain. Augustus, founder of the empire (in the political rather than military sense), completed the conquest of Spain, subdued the Alpine tribes, and pushed the boundaries of Rome to the Danube. His generals invaded Germany and crossed the River Elbe. But Rome’s hold was broken by the Varian disaster of AD 9. Augustus was an old man when he gave the advice to his successor, Tiberius, not to expand the empire further. In Germany, however, as elsewhere, the legions remained in their bases waiting for the order to advance – an order which never came. Gradually the army settled down on borders which had began as pause-lines in a hitherto unstoppable advance.
Thereafter, the Roman frontiers waxed and waned. These movements are helpful both in dating frontiers and determining their development. The first step toward the creation of a frontier, it would appear, was for auxiliary units to be spread along the border – perhaps this helped the supply of provisions to the troops as well as improving control on the frontier line. There was consolidation of a different kind with the construction of a road between the Rhine and the Danube under Vespasian to aid communication between the two frontier provinces of Upper Germany and Raetia. This was followed by the construction of towers. The Romans constructed towers for different purposes, but the aim now was to maintain observation, and thereby control, along the boundary of the empire.
This development should be seen in the context of two statements of the Roman historian Tacitus. These make clear that it was usually only possible for the German tribes to enter the empire unarmed, under guard, and after paying a fee; and, given the bureaucratic and relatively uniform nature of Roman society, it is likely that such regulations operated elsewhere.
The military installations on the frontiers grew in number and complexity as the years passed. Large forts were supplemented by smaller forts, fortlets, and towers. Under Hadrian, of course, there was a further development: the addition of linear barriers in certain areas. The first to have been constructed was, it appears, in Germany, linking the upper reaches of the River Rhine to the Danube.
From Germany, Hadrian travelled to Britain, where, it is recorded in a questionable biography written 200 years later (but the only one of him we have), that ‘he was the first to build a wall 80 miles long from sea to sea to separate the barbarians from the Romans’. The order of construction of Hadrian’s Wall was worked out from the evidence of building work and inscriptions in the early years of the 20th century. It became clear that there were two main building phases. In the first, the plan was a continuous linear barrier with a gateway every mile and two towers in between. The purpose would appear to have been to divide ‘them’ from ‘us’ – as Hadrian’s biographer attests.
But before that scheme was completed, forts were constructed on the line of the Wall, at first actually astride the barrier. We see here two separate functions, frontier control and military defence. Thereafter these two functions became intertwined in Britain, with the forts based on the linear barrier both on Hadrian’s Wall and the Antonine Wall, whereas they lay behind the frontier in Upper Germany and Raetia.
While the border in Europe mainly followed the Rivers Rhine and Danube, with the head waters linked by an artificial frontier, the southern frontier mostly faced the Sahara Desert. Even here, linear barriers were constructed to control the movement of people, perhaps in this case mainly nomads moving their flocks from one pasture to another. And in the Carpathian Mountains, which surrounded the province of Dacia north of the Danube, the passes were blocked by short lengths of wall.
Many of these frontiers survived for centuries. Certainly, the artificial barrier between Upper Germany and Raetia was abandoned in the AD 260s, and the whole of Dacia in the AD 270s, but the new frontier line, which followed rivers again, was fortified with the usual range of forts, fortlets, and towers. These continued to be built into the 4th century AD. A splendid series of towers of otherwise ruinous forts survives in Austria, as do free-standing towers erected by the Emperor Valentinian I (AD 364-375) in Hungary.
The end came in different ways, but the crossing of the frozen River Rhine on the last day of AD 406 by a force of Suebi, Vandals, and Alemanni marked the beginning of the end of the Western Roman Empire. The frontier installations were swept aside, as they had been on previous occasions – a sharp reminder that their purpose was frontier control: the defence of the empire rested on the power of the army in fighting – and winning – pitched battles.
Research on the Roman frontiers continues. Excavations on both Hadrian’s Wall and the Antonine Wall have revealed the existence of pits on the berm, the space between the wall or rampart and the ditch. At Byker, on Hadrian’s Wall, the pits were arranged in three rows, each containing two posts, probably the trunks of trees with their branches cut back and sharpened. This discovery has prompted a review of the purpose of Hadrian’s Wall: how far was it a heavily defended frontier line, or were these merely the equivalent of trip wires such as are used on modern frontiers?
Aerial survey has long been used to provide new information about Roman frontiers. On the eastern frontier, Antoine Poidebard recorded the military remains of Syria from the air in the 1920s, providing an invaluable record of the greatest value today. Of equal significance was the work of Jean Baradez on the Fossatum Africae in North Africa.
It took the end of the Cold War in 1989-1990 to bring the benefits of aerial archaeology to Central and Eastern Europe, and with it a further impetus to international co-operation. One interesting development is the discovery of a camp in Slovakia which takes Roman campaigning almost to the border of Poland. On the Antonine Wall, uniquely, the labour camps discovered from the air help us to understand better the building arrangements for that frontier.
More recently, geophysical survey has become an important tool, not just in planning the interior of forts, but, more significantly, what was happening outside. We have discovered that the civil settlements which grew up around forts were much larger than previously envisaged, and that beyond them lay boundary ditches and field systems.
Dendrochronology is another key tool. A date of AD 72/73 for a timber from Carlisle in North-West England has opened up the possibility of re-dating Roman campaigns into Scotland. A recent dendrochronological date from a timber on the German frontier shows that it was felled in AD 119/120. The only snag is that the date is one year earlier than Hadrian’s visit in AD 121! And a series of dates for the replacement of this Hadrianic frontier shows that it was constructed, at least in Raetia, in the early AD 160s.
Two remarkable aspects of modern frontier studies are, first, that several long-standing problems remain open to discussion, and second, that new problems keep popping up. You might have thought that someone would have studied how Hadrian’s Wall was surveyed. In fact, nothing was done until very recently: John Poulter’s fascinating conclusions are to be published this summer by British Archaeological Reports.
Among the old problems is the ‘Mommsen conundrum’. 150 years ago, Mommsen compared the German and British frontiers and suggested that the latter were more heavily defensive because they were continually under threat from the untamed Highlanders. I would argue, on the other hand, that the design of Hadrian’s Wall was the direct result of Hadrian’s intervention and that this was the reason for its distinctive form (see the next issue of Archaeologia Aeliana for a full discussion).
Towards WHS status
Many Roman military sites are displayed to the public. Opening such remains to the depredations of the weather as well as visitors creates a need for continual maintenance. In some cases, modern intervention to repair the damage of earlier consolidation leads to new discoveries, as is happening at present at the fort at Eining in Bavaria.
Frontiers usually divide people, but the modern study of the Roman frontiers is actually bringing countries and scholars together – not just those through whose territory the frontiers actually ran, but also those with artefacts in their national museum collections which have sometimes travelled very far from their places of origin. The creation of a new type of World Heritage Site that will encompass all the frontiers of the Roman Empire is an attempt to consolidate and develop a growing multinational project for the study and display of what may be the greatest system of border defences in human history.
This article is an extract from the full article published in World Archaeology Issue 35. Click here to subscribe