Traditionally, historians reckoned that these walls were constructed to deter an invading army. The Romans had stopped their northward expansion at this point because of the fierceness of the Scots.
Recent reconsiderations of Hadrian’s wall, however, have raised the notion that the wall would not have been an effective barrier to a large military force, especially because it has gates at intervals along its length. The numbers of Roman soldiers stationed along the wall also would not have been sufficient for the purposes of repelling a large-scale attack.
If not strategic defense, what, then, was the purpose of the wall? Historian Andrew Curry asks:
If the walls weren’t under constant threat, what were they for?
Although scholars are diligent in their efforts to be objective, they are nonetheless affected in many and subtle ways by their time and by their location as they study events in other times and other locations.
Perhaps those who hypothesized about Hadrian’s Wall were retrojecting geopolitical patterns from their own era onto the earlier Roman era. Andrew Curry writes:
Ever since British antiquarians organized the first scientific excavations along Hadrian’s Wall in the 1890s, historians and archaeologists have assumed Rome’s walls were military fortifications, designed to fend off barbarian armies and hostile invaders.
The wall seems to constitute a sealed border, Romans to the south, Scots to the north. Why, then, the gates? Why no evidence of massive battles along the wall?
The wall was of a physical size and shape that a large invading army could easily scale it with ladders or ropes, and doing so in large numbers, would easily be able to overwhelm the few soldiers stationed there.
For decades arguments focused on tactical details: Did soldiers stand along the wall to rain spears and arrows down on invaders or sally forth to engage the enemy in the field? The trenches of WWI — and the deadly back-and-forth battling of WWII — did little to change the prevailing view of the ancient frontier as a fixed barrier separating Rome from hordes of hostile barbarians.
Perhaps Hadrian’s Wall was less like the ‘Iron Curtain’ border between East and West Germany during the Cold War, and more like the wall which divided East and West Berlin. The former was in anticipation of large-scale military formations and attacks, the latter was designed to prevent individual defectors or smugglers, or those in very small groups.
These same questions can be raised about other Roman borders, like the Limes fortifications and walls between the Rhine and the Danube in central Europe. Historians face divergent paradigms in thinking about the Roman frontiers.
Archaeologists studying the frontiers in the 1970s and ’80s later found that the Iron Curtain dividing Europe had shadowed their view of the distant past. “We had in Germany this massive border, which seemed impenetrable,” says C. Sebastian Sommer, chief archaeologist at the Bavarian State Preservation Office. “The idea was here and there, friend and foe.”
How were the relations across the border at the frontier? Were the Scots north of England, or the Germanic tribes northeast of Gaul, regarded as enemies simpliciter?
Or was there mutually beneficial trade between local farmers and villages on both sides of the borders? It is known that the Romans sometimes hired mercenaries from among those on the other side of the border. This would indicate that the border had more the character of an administrative structure than of a sworn blood feud.
Today a new generation of archaeologists is taking another look. The dramatic, unbroken line of Hadrian’s Wall may be a red herring, a 73-mile exception that proves an entirely different rule. In Europe the Romans took advantage of the natural barriers created by the Rhine and Danube Rivers, patrolling their waters with a strong river navy. In North Africa and the eastern provinces of Syria, Judea, and Arabia, the desert itself created a natural frontier.
The Roman border guard may have been more about monitoring roads and commerce than about confrontations between massive armies.
Taxes and tariffs were an important source of income for the imperial government, a purpose for which it would gladly spend the money needed to keep soldiers stationed along the border. Was their main purpose perhaps tax collection?
Military bases were often ad hoc installations set up to watch rivers and other key supply routes. The Latin word for frontier, limes (LEE-mess), originally meant a patrolled road or path. We still use the term: Our “limits” comes from limites, the plural of limes.
Perhaps the detachments who served along the border were more like customs officials than a strategic defense. The Romans would want to keep an eye on the people and merchandise which entered and left their empire.
Artifacts show that there was substantial trade across the borders of the empire. Roman products are found deep into Germanic territory; Germanic products, like amber from the shores of the Baltic, are found deep in Roman territory.
Outposts on rivers like the Rhine and Danube or in the deserts on Rome’s eastern and southern flanks often resemble police or border patrol stations. They would have been useless against an invading army but highly effective for soldiers nabbing smugglers, chasing small groups of bandits, or perhaps collecting customs fees. The thinly manned walls in England and Germany were similar. “The lines were there for practical purposes,” says Benjamin Isaac, a historian at Tel Aviv University. “They were the equivalent of modern barbed wire — to keep individuals or small groups out.”
In the empire’s later centuries, there was a need for workers in the Roman provinces, and slave or servants were imported from outside imperial borders. But the bureaucrats of the empire would want to know who, and how many, and from where these servants came.
Both observing and controlling the flow of people and goods across the borders would be important to Roman economic policy.
Isaac argues that the frontiers resembled certain modern installations more than thick-walled medieval fortresses: “Look at what Israel’s building to wall off the West Bank. It’s not meant to keep out the Iranian army, it’s made to stop people from exploding themselves on buses in Tel Aviv.” Warding off terrorists may not have motivated the Romans, but there were plenty of other factors — as there are today. “What the United States is planning between itself and Mexico is substantial,” says Isaac, “and that’s just to keep out people who want to sweep the streets in New York.”
The outposts along the borders may have had as goals, in addition to monitoring and regulating trade, expanding trade. A permanent and official presence at the outer limits of the empire may have been meant to encourage traders from deep inside Germanic or Scottish territory to bring their wares for trading.
Roman coins have been found, e.g., on the Scottish island of North Uist, almost unimaginably far north of Hadrian’s Wall.
More archaeologists are endorsing that view. “Isaac’s analysis has come to dominate the field,” says David Breeze, author of the recent Frontiers of Imperial Rome. “Built frontiers aren’t necessarily about stopping armies but about controlling the movement of people.” The Roman frontier, in other words, is better seen not as an impervious barrier sealing Fortress Rome off from the world but as one tool the Romans used to extend influence deep into barbaricum, their term for everything outside the empire, through trade and occasional raids.
In Denmark and Sweden, archeologists have found Roman coins. Although we must exercise caution in drawing conclusions from the these finds - we don’t know how or why those coins came to be in those locations - these finds indicate at least the probability of widespread Roman trade beyond the borders of the empire.
Might we conjecture that a Roman merchant would venture past the lines which marked the edge of the empire? Profit would be a powerful motive for such travels. Likewise, Germanic and Scottish traders, we can say with certainty, entered and left the empire on a regular basis to peddle their wares.