Hadrian’s Wall: What Was It For, and Why Was It Built?

The Romans saw ancient Britain as a mysterious island at the edge of the known world. Julius Caesar made an initial attempt to reach her shores on an expedition in 55-54 BCE. But the Romans did not manage to launch a successful invasion of the island until the summer of 43 CE. Under the command of Emperor Claudius, general Aulus Plautius, along with around 40,000 legionary soldiers, invaded southern Britain. By early 44 CE, Britain had become another province of the Roman Empire, under the name Britannia.

In 122 CE, Emperor Hadrian visited Britannia. Later that year, building began on the structure which we know today as Hadrian’s Wall. This Wall created a physical, artificial frontier that did not exist anywhere else in the Empire. The primary phase of the Wall took over four years to complete and was an immense project involving many thousands of men. But what exactly was this complex and unique structure, and why was it built?

The Wall was located in modern-day northern England. At its longest, it measured 118 kilometers and stretched from Wallsend-on-Tyne in the East to Bowness-on-Solway in the West. The Wall itself was built of stone blocks, but its size varied along the route. The eastern section was approximately 3 meters wide and 4.2 meters high, but the western section was 6 meters wide and 4.2 meters high. The final 6 kilometers of the Wall in both eastern and western directions were built last. Here, the width was reduced to just 2.5 meters.

There was also a V-shaped ditch running in front of the Wall, which was 8.2 meters wide and 3 meters deep. A vallum was also built behind the forts on the Wall for extra security. This was essentially a turf rampart with palisades at the top, which was 6 meters wide and 3 meters deep.

Forts, mile castles, and turrets were positioned at regular intervals along the Wall. Mile castles (fortified gateways) were located every Roman mile (1481 meters) and turrets (observation towers) were every third of a Roman mile (494 meters).

Forts provided living quarters for units of soldiers as well as storage and administration buildings. Many of the forts connected to Hadrian’s Wall were actually built before the Wall became a formal structure and frontier. Some older forts were located in front of the Wall. These included outpost forts, such as those at Bewcastle, Birrens, and Netherby. These forts were not permanently inhabited but provided a strategic base for campaigns to the North. Sixteen forts were placed on the route of the Wall and the remainder were behind it on the Stanegate. This was a road built in Emperor Trajan’s reign (98-117 CE) connecting forts from Corbridge to Carlisle.

“Hadrian was the first to build a wall, eighty miles long, to separate Romans from barbarians”
(Scriptores Historiae Augustae, Vita Hadriani 2.2)

This is the only known ancient extract to explain why Hadrian’s Wall was built (Breeze and Dobson, 2000). The creation of a physical boundary to protect the Romans from their enemies is perhaps the most obvious reason for building the Wall. But who exactly were these ‘barbarians’?

When the Romans arrived in the 1st century CE, ancient Britain was inhabited by various tribes, each controlling their own particular area of the island. Not all of these tribes surrendered their homeland easily and pockets of hostility remained throughout the 400 years of Roman occupation. Among the most belligerent were the tribes of Caledonia, modern-day Scotland, known for their warlike and fearless spirit.

Caledonia comprised much of the area north of the Wall and the main tribes living there were the Caledonii and the Damnonii. These people were of Celtic origin and had social and trade links with the Gauls of modern-day northern Europe. The battle tactics of the Caledonian tribes were ruthless and their weapons were brutal. The Romans were never able to defeat them entirely and uprisings regularly flared up. Some progress was made in the 80s CE, but by Emperor Trajan’s reign, the Romans had retreated out of Caledonian lands.

When Hadrian’s Wall was built in 122 CE it helped to protect the Romans from the barbarians of Caledonia. But it also served to separate tribes on both of its sides. In time, the lack of communication between the tribes of Caledonia and northern England led to an overall decrease in tribal power.

Initially, the Wall was intended as a base from which to launch necessary expeditions into Caledonia. But, over time, it also became a border at which to monitor the movement of people and trade, which also created a point of taxation.

Interestingly, another wall was soon built 100 miles further north during the reign of Hadrian’s successor, Emperor Antoninus Pius (138-161 CE). The Antonine Wall was half the length of Hadrian’s Wall since it was constructed at the narrow point between Bridgeness in the east and Old Kilpatrick in the west. The definitive reason for building this new wall is unknown, but some historians believe that it points to Hadrian’s Wall’s failure as an effective defensive barrier (Breeze and Dobson, 2000). Nevertheless, the Antonine Wall was abandoned in the 160s CE and Hadrian’s Wall was back in constant use for the next 200 years.

Emperor Hadrian ruled the Roman Empire from 117 to 138 CE. Before his accession to power, he held a number of elite political positions and was a member of Emperor Trajan’s campaign staff. But Hadrian was also known as a cultured, academic man who was fascinated with the sophisticated Greek world throughout his life.

Soon after becoming emperor, Hadrian withdrew Roman military presence from the East. His predecessor, Trajan, had been campaigning against the Parthians of modern-day Iran from 114 to 117 CE. But Hadrian believed that these conquests were untenable. Instead, he wished to establish control over what already existed of the empire and usher in an era of stability and peace. Hadrian’s Wall was built in accordance with this new foreign policy (Breeze and Dobson, 2000). Its vast frontier created a limit to the empire and, consequently, a limit to its expansion.

So did Hadrian’s Wall make Britannia a more peaceful and stable province? This is a complex question to answer but the Wall certainly did not eliminate military activity entirely.

Examples of this include the campaigns of Emperor Septimius Severus from 209 to 211 CE. As we have seen, the tribes of Caledonia north of the Wall were continuously hostile towards the Romans. In 208 CE, Emperor Severus decided to try to do what no emperor had been able to do before; conquer Caledonia once and for all. So he launched a large invasion with 50,000 men which was initially successful. But it was a brutal campaign with harsh weather and difficult terrain. A tenuous peace treaty was agreed but uprisings soon resumed. Then, in early 211 CE, Severus suddenly fell ill and died. His sons, Caracalla and Geta, decided to leave unruly Caledonia behind and retreated back behind the Wall.

Units from various Roman legions came to Britannia from across the empire to construct the Wall in the 120s CE. By the end of Hadrian’s reign, garrison troops posted on the Wall were between 9,000 and 15,000 men. Initially, it was auxiliary regiments who were sent to the Wall but in later years legionary units were also present. Dedicatory inscriptions provide useful information about the diverse military presence in the forts along the Wall. The evidence includes votive altars and tombstones dedicated by men who were native to places such as the Netherlands and even Syria.

One of the primary reasons the Wall was built was to provide a major base for the Roman military throughout the province. But it is also important to note that some Roman soldiers spent years of their lives on the Wall. For many, it would have become not just a place of work but also a home.

Military forts on Hadrian’s Wall were more like small fortified towns. As well as sleeping barracks, forts would also include hospitals, granary barns, sacred chapels, and administration buildings. There was often even a grand villa for the commander and his family. One of the best-documented forts on the Wall is Vindolanda, located on the Stanegate road 25 miles east of modern-day Carlisle.

From the 1970s onwards, hundreds of well-preserved wooden writing tablets have been discovered at the site. The tablets date from around 90 to 120 CE when the fort was occupied by Cohors I Tungorum and Cohors IX Batavorum. These tablets include the largest discovery of Roman letters to date and they provide a fascinating insight into daily life on the Wall. There are task lists and inventories but also personal letters written between friends. There is even a birthday invitation written from the wife of one high-ranking soldier to her sister (as pictured above).

After the successful invasion of 43 CE, Roman culture gradually began to permeate the tribal lands of ancient Britain. The Romans tried to create harmony between conquerors and conquered through a process historians today call ‘Romanization’. This process involved introducing elements of Roman culture to the local population while not forcefully suppressing the indigenous way of life.

The Roman historian Tacitus is the main source on the policy of Romanization. He presents a cynical and biased view of the concept in his biography of Agricola, who was governor of Britain from 78 to 84 CE.

‘(Agricola) wanted to accustom them (the Britons) to peace and leisure by providing delightful distractions…the naïve Britons described these things as ‘civilization’, when in fact they were simply part of their enslavement’.
(Tacitus, De Vitae Agricolae)

Architecture was an important part of Romanization. Temples were built as a way to encourage interest in Roman gods. However, the Romans did not prevent the British from worshiping their own gods. Theatres and amphitheaters encouraged participation in Roman entertainment. New towns with public baths and shops also offered access to a more sophisticated way of life. These were all used as vehicles for winning over the local population.

Hadrian’s Wall would have been a powerful catalyst for Romanization since it was responsible for bringing thousands of Roman soldiers to Britain. These men brought with them their food, clothes, religion, and even cooking utensils. All of these cultural markers would have had a lasting impact on the people of Britain. Soldiers also infiltrated their way into the local population through marriage. There are many examples of Roman soldiers marrying local women and staying in Britain after service to make a life for themselves.

As we have seen, Hadrian’s Wall was built primarily as a frontier to the Roman Empire. This frontier provided protection from hostile enemies and a base for military units. But the Wall was also a lasting monument to Hadrian, an emperor who valued peace and stability over military expansion and personal triumph.

Hadrian’s Wall represented the very best of Roman engineering and infrastructure. The sheer size and permanence of the Wall along with its military presence, would have served as a constant reminder to the local population that they lived under Roman control. Much of the success of the Roman Empire was due to the ability to subdue local populations and create stable provinces effectively. The presence of the Wall, arguably, contributed much to the success of Roman occupation in Britain, which lasted for over 400 years.