Hadrian's Wall and Free Trade

Of the many civil engineering feats performed by the Romans, Hadrian’s Wall is one of the most famous: it stretches over seventy miles across the island of Great Britain, from east to west, from one coast to another.

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.

Roman Walls

The Roman Empire, having risen around 27 B.C. from the remains of the Roman Republic, expanded and reached its largest size in the middle of the second century, around 150 A.D., give or take a few decades. Having occupied such a large area of land, it needed to defend and hold that land.

The momentum of expansion dwindled and was redesigned into the momentum of defense. The Roman military had formerly focused on conquering new land and transforming such land into integrated provinces of the Empire. Now, the military was more interested in ensuring that competing powers - like the Germanic tribes, the Scots, and the Irish - did not expand into Roman land.

In addition to stationing garrisons along the border, the Romans, ever the good engineers, undertook another amazing building project: a series of walls which would eventually stretch for hundreds of miles along selected segments of the empire’s borders.

The empire sprawled across Africa, Asia, and Europe, and included islands like Great Britain. The borders totaled thousands of miles. Historian Andrew Curry describes how

A stunning network of walls, rivers, desert forts, and mountain watchtowers marks Rome’s limits. At its peak in the second century A.D., the empire sent soldiers to patrol a front that stretched from the Irish Sea to the Black Sea as well as across North Africa.

As a percentage of the total imperial border, the walls were a small fraction, built where strategists figured they were most needed. The engineering precision is impressive. In one case, a 31-mile stretch of wall is almost perfectly straight, deviating merely 36 inches. The design of the wall is precise and crisply geometrical. The exact shape of the wall varies: Hadrian’s Wall between England and Scotland is a different structure than the Limes wall in Germany.

Why did the Romans build the walls? To protect a regime besieged by barbarians, or simply to establish the physical edge of the empire?

The walls were only a small part of the border system. More often, there were watchtowers spaced at intervals. How porous were these borders? Certainly, local Germanic and Celtic tribesmen in central Europe were used to trading with each other, and if a Roman border ran between two small settlements, that would have meant little to them, and little to the Roman military men stationed there. The borders were most likely surveilled for the purposes of watching for major military movements.

But such imperial thinking was foreign to the original Roman Republic, a governmental structure dating from around 509 B.C., and designed to administering a city-state and a few agricultural lands surrounding it. The Republic’s success in expanding would also be its downfall.

From around 500 B.C., Rome expanded continually for six centuries, transforming itself from a small Italian city-state in a rough neighborhood into the largest empire Europe would ever know.

The Republic was not capable of effectively governing this large territory. The Empire replaced it.

The emperor Trajan was an eager heir to this tradition of aggression. Between 101 and 117, he fought wars of conquest in present-day Romania, Armenia, Iran, and Iraq, and he brutally suppressed Jewish revolts. Roman coins commemorated his triumphs and conquests.

Trajan left a gigantic empire to his successor. Had Trajan lived longer, he might have learned that the empire was perhaps too big to be thoroughly organized and successfully defended.

The military requirements - defending borders in England, across central Europe, into southwestern Asia, and across northern Africa - were enormous. Too big, in fact. The regular Roman army was supplemented at first by domestic mercenaries, then by foreign mercenaries. But this help was often actually another problem.

When he died in 117, his territory stretched from the Persian Gulf to Scotland. He bequeathed the empire to his adopted son — a 41-year-old Spanish senator, self-styled poet, and amateur architect named Publius Aelius Hadrianus. Faced with more territory than Rome could afford to control and under pressure from politicians and generals to follow in the footsteps of his adoptive father, the newly minted emperor — better known as Hadrian — blinked. “The first decision he made was to abandon the new provinces and cut his losses,” says biographer Anthony Birley. “Hadrian was wise to realize his predecessor had bitten off more than he could chew.”

The Romans had ventured northeast of the line on which the Limes wall would eventually be built. The earliest walls had actually been built as far back as the reign of Octavian-Augustus, who suffered a humiliating defeat in 9 A.D. at the hands of the Germanic tribes.

Under Hadrian's rule, they would pull back a few miles to more defensible positions.

But under Hadrian and his successor, the Limes boundary line, roughly the southwest border of Germany, would reach its full structural development of walls, watchtowers, and forts.

The new emperor’s policies ran up against an army accustomed to attacking and fighting on open ground. Worse, they cut at the core of Rome’s self-image. How could an empire destined to rule the world accept that some territory was out of reach?

As it turned out, the Roman Empire had not only stopped its expansion, but it was preparing to shrink. The Germanic tribes in Europe, and the Scots in Great Britain, became bolder and more familiar with Roman military practices. Knowledge of the Romans allowed the tribes to strategize ways to outmaneuver and outfight the Romans.

The Limes marked the highpoint of the empire, but at the same time marked the beginning of the end.