There are two ways of looking at Hadrian’s Wall. The first is as part of the network of frontier systems that girded the Roman Empire. During Hadrian’s reign, these stretched for roughly 13,000km through 20 modern countries on three continents. Set against that whole, the 117km length of Hadrian’s Wall looks pretty puny. But these frontier systems were not identical, and the Wall stands out from its peers by virtue of its scale. Take the linear barrier that was installed during Hadrian’s reign along the frontier in Upper Germany: a timber palisade, perhaps standing about 3m high. While this was still a stout obstacle, it is in a completely different league to the linear barriers that existed along Hadrian’s Wall. By the end of Hadrian’s reign, these comprised a ditch that averaged over 8m wide and 2.7m deep, a curtain wall probably rising roughly 4.3m to wall-walk height, and an enigmatic earthwork called the Vallum presenting a 36m-wide obstacle to the south. In places, spiky wooden obstacles festooned the berm between the ditch and curtain with the Roman equivalent of barbed wire.
As a formal frontier system of some kind is only to be expected in Britain – as elsewhere on the edges of empire – during this period, it has been proposed that the abnormal scale of the Wall is simply a flourish: a hollow piece of imperial rhetoric, serving no practical purpose beyond expressing the might of Rome. As we have seen, though, while the Britons appear ill equipped to hold their own against the Roman army in set-piece battles, they could inflict losses during hit-and-run attacks. The more dispersed military deployments visible in Wales, Scotland, and on the Tyne–Solway isthmus make sense as attempts to neutralise this threat. If so, it follows that efforts to counter British warriors were shaping military networks in the decades leading up to Hadrian’s visit. This brings us to the second way of viewing the Wall: as a control system whose design was a calculated response to the cocktail of violence served up in Britain during Hadrian’s reign.
A link between warfare and the Wall is made explicit by the reconstructed text of a Roman inscription found at Jarrow. This probably once graced a victory monument and declared that ‘after the barbarians had been dispersed and the province of Britain had been recovered, he [presumably Hadrian] added a frontier line between either shore of the Ocean for 80 miles’. Taken at face value, this makes it plain that fighting formed the backdrop to the Wall’s origins. Yet, while there is abundant evidence for combat in Britain at around this time, we lack the details that the ancient literature furnishes for the Boudican revolt and Mons Graupius. Instead, events can only be loosely reconstructed by assembling a patchwork of different types of evidence. Drawing these threads together presents a picture of serious Roman troop losses. Our challenge is understanding the relationship between the military situation in Britain and the genesis of the Wall.
