Everybody in Britain is aware of that long ribbon of rock that stretches 73 miles from the east to the west coast, dividing the border of England and Scotland. Except that it doesn’t really divide the border – being somewhat to the south of the modern-day line on a map. Everybody has seen pictures of the majestic and impenetrable curtain wall, standing many metres high, and crowned by imposing crenellations from behind which, Roman soldiers would fire their arrows at those pesky oncoming barbarians. Except that all that remains of the wall are foundations, and some well-made replicas. And everybody knows that it provided an impregnable stone barrier, protecting Roman interests to its south. Except that large parts were actually nothing more than turf mounds a couple of metres high. There are a lot of myths and legends associated with Hadrian’s Wall, but it is safe to say that the placement of such a unique structure within the Roman Empire has given those living on these islands an over-inflated impression of the importance that they had within the vast imperial domain.
Strangely, one fact that is little recognised outside of the history community is that historians and archaeologists really don’t know what this cast construction project was actually for. This might seem strange, but do stick with me.
The most obvious suggestion is that Hadrian’s Wall is a defensive installation, as noted above, to keep out barbarian incursions from the north. But there are several issues with this assumption. Firstly, many parts of the wall were downgraded during the construction process to be much thinner and shorter than the original plans, reducing its defensive capabilities. Furthermore, as mentioned above, stretches of it were only a couple of metres high and built from turf. Hardly the material of an impregnable barrier. Secondly, along the 73 miles of its length, there are no fewer than 80 milecastles, and 17 forts, each with gates for passage through. That is significantly porous for something intended to keep people out, and quite simply put, would be phenomenally inefficient by Roman standards.
With that in mind, it is often suggested that the Wall was a mechanism for controlling access and egress to and from the Empire, which is a fairly sensible suggestion. Particularly as the Romans loved to impose taxes upon goods entering and exiting their Empire. But that is only until you observe the placement of many of those gates. They occupy the most baffling positions with some on the tops of hills, and others adjacent to vertical cliffs. This does make one wonder whether those planning the wall knew, or indeed cared, where they were to be placed, or if they were simply following the edict of the Emperor who commissioned its construction. This would be much like the legend of the Tsar’s finger and the Trans-Siberian railway, in which Tsar Nicholas I was said to have drawn a line across his Empire with a pencil and a ruler to show where he wanted the route, but his finger caused a bump in the line. The designers, fearful of reprisal, dared not question this mistake and so it was included as per the Tsar’s faulty drawing. Perhaps Hadrian simply declared that he wanted a fort every mile, and the engineers simply followed his word to the letter, regardless of context. Even so, this does somewhat undermine the idea that the Wall was intended as some kind of official border control mechanism.
Historians also consider the context of the Roman Empire during this time to try to seek an explanation for the Wall. Hadrian’s predecessor, Trajan, had expanded the Empire to its greatest extent in 117 AD, and was respected as a military leader and conquered. Whilst Hadrian was similarly respected amongst his troops, his long reign was marked by considerable relative stability and peace both within the Empire, and at its borders. Yet he had inherited the same army that had spent the better part of a century wandering around Europe and conquering vast swathes of territory. This was no small band of fighters either, but an enormous and disciplined mass of just less than half a million men. It could hardly be justified to allow such a number to simply sit in camps, twiddling their fingers for decades on end. Plus, restless soldiers had in the past found new ways to occupy themselves by plotting military rebellions. It would be quite understandable if Hadrian had taken the strategic decision to keep the 15,000 or so men that are thought to have been required to construct the wall busy in the task of doing so. Furthermore, continuous maintenance and manning would have tied up thousands of otherwise idle solders for decades more.
Another thought is that the Wall was simply a demonstration to the unruly indigenous population of the northern British Isles – showing that the might of Rome could reach even into the furthest corners of its empire. Just like the White Tower in London let the Southerners know not to mess with William the Conquerer, would those under the yoke of Roman rule dare to threaten an imperialist machine that could create such an imposing structure of power in such a short period of time?
The reality is, we do not really know what Hadrian’s Wall was for. There is surprisingly little physical evidence to help us, other than to point us towards the superficial suggestions above, which are each problematic in themselves. Even more surprisingly, considering the enormous importance that is placed upon the Wall in British culture, and how it is used as a demonstration of the importance of the British Isles within the Roman Empire, it does not seem really to have registered with Romans of the period. In the entire body of Roman writing, there is only one singular piece of literary evidence that Hadrian had built the wall, and that resides within the notoriously unreliable Scriptores Historiae Augustae which post-dates the reign of Hadrian by a couple of centuries or so. Surely had it made an impact upon Roman minds of the day, reams of information would have been available on the subject.
My best guess is that Hadrian’s Wall is likely a little bit of everything mentioned above; it was a multi-purpose construction that could serve simultaneously as defensive barrier, border control, endless task for a restless army, and a signature of power to the locals. It may not have been perfect in any one of these functions, but if any civilisation understood the efficiency of using a single structure for a multitude of purposes, it would have been the Romans.