Hadrian's Wall marked a turning point in Roman Britain. It marked the point at which the Romans first marked a limit to their conquest of Britain. Although the Romans would advance again into Scotland and build the Antonine Wall, the advances were short lived and within a few decades the border was again back on Hadrian's Wall; where it would stay until the very end of the Roman occupation of Britain.
Why was Hadrian's Wall built?
Hadrian was the first to build a wall, eighty miles long to seperate the Romans from the barbarians.
Apart from this short statement from the Scriptores Historiae Augustae, the Romans left no words to tell us what the Wall was for. Various reasons have been propose, was it to mark the extent of Empire, a customs barrier, a defense to keep the Picts out or a mixture of these? In all probability the Wall served all these purposes the role may well have fluctuated depending on the actual situation at the time.
Although the Romans developed fixed defenses to protect their borders throughout the Empire, Hadrian's Wall is unique in it's strength. It does in-fact seem to be an awful lot of troops just to maintain a customs barrier and so the Wall must therefore have had a defensive role to play. However even in a military role it should not be seen in the manner of a medieval castle with troops repelling the enemy from the battlement. It would have served rather as a stop to the enemy, who could then have been brought to battle by the garrisons from the forts along the Wall.
Why was it built here?
Whatever the exact reason for building the Wall, the reason as to where is is much simpler to answer as it is the narrowest part of the country and the central part follows a natural ridge
For despite forays into Scotland and it's occupation nearly forty years before, the Roman's had been unable to consolidate their gains and had been slowly withdrawing southward. The Romans had pressing needs for troops throughout the Empire and the extra numbers needed to hold onto the North would in no way have justified the economic gains. Hadrian's Wall actually lies at the Half Way point in Britain, by road about 350 miles north of the Channel and slightly more than this south of John O'Groats. With the terrain increasingly mountainous, boggy and wild it is very difficult to see how the Romans could have ever hoped to control the entire country without adding at least another legion to the garrison of Britain ).
Agricola, the governor of Britain, had invaded Scotland he had four legions at his disposal but soon afterwards one of theses legions (the II Adiutrix) was urgently needed on the Danube (It may have also been true that the Emperors were also nervous about leaving four legions under the control of one governor). The three legions left were not enough to occupy the entire island and so over the next forty years there was a process of the Romans slowly withdrawing from Scotland, first evacuating forts to the north of the Forth-Clyde line (roughly Glasgow to Edinburgh) and then moving back to the Tyne-Solway line. The Romans would have left client kingdoms to the north of this line to control the region and they may indeed have seen the movement as temporary.
This pull-back continued further under the Emperor Trajan and the number of forts to the north of the Tyne-Solway line declined even further and the main frontier line was consolidated on to the Stanegate road, which runs just a few miles south of where Hadrian's wall was to be built.
The Romans policy of slowly withdrawing from Scotland may have been seen as a sign of weakness by some of the tribes, in any case we do know that there was major fighting in Britain during Hadrian's reign (Trajan's sucessor). It is likely that this fighting was behind Hadrian's visit to Britain in 122 AD (although some historians believe that the fighting was actually as a result of hostility to Hadrian's Wall being built (an extreme case of nimbyism perhaps and an issue that modern planners might well understand!)
Hadrian must have known of the plans to deal with the situation in Britain before his visit to his province. There is even some evidence that he may have stayed at Vindolanda during his tour and from where he would have been in a prime position for it's planning. It is possible that the extent of the fighting in Britain may well have been deliberately exaggerated to justify the immense cost of the project.
When was it built?
Work started on the Wall in AD122.
How long it took to build is uncertain, although the fort at Great Chester was built in 128AD and Carrawburgh in the early 130's. The first five miles of the turf wall was rebuilt in stone towards the end of Hadrian's reign. It is likely then that most of it was completed within six years, but with work continuing right to the end of Hadrian's life.
It wasn't until the abandonment of the of the Antonine Wall that the turf Wall was completely rebuilt in stone, along with magnificent new bridges at Corbridge and Chesters. There was further major work on the Wall in the early 3rd century when many of the turrets were removed.
Why a wall?
Hadrian decided to solve the problem by building the Wall, a project without precedence in Europe and one far exceeding the size of any previous fortifications.
This grand idea of a wall would have matched Hadrian's character and his desire to stamp his personality on the Empire. He had already decided to adopt radically different policies from his predecessors and instead of expanding the Empire he had decided to consolidate it. From his reign the Empire effectively stopped expanding and the emphasis moved on to the defensive. The idea of a colossal fixed boundary in the far north of his Empire would have fitted ideally with Hadrian's new policy.
It is likely that whatever the need for building the Wall, that need must have been pressing rather than urgent. The Wall would have taken years to build and if the danger had been imminent then you would expect hastily erected earthworks to be thrown up to deal with it. Whatever the crisis that prompted it must already have been been dealt with, so if it was built as a defensive measure then it resembles the Maginot line built after the First World war rather than the trenched built during it.
The Wall does also reflect a problem the Romans had politically. The Roman armies concentrated on defending the frontiers rather than positioning large powerful armies to respond to attacks. This was because of the Roman Emperors deep and well founded mistrust of their generals along with a constant fear of mutiny in their armies. This meant that the Emperor could not tolerate a large army under a powerful general and preferred to have smaller forces spread out along the frontier.
The prestige of the Roman Emperors was always critically important in ensuring they kept hold of power (and their lives!) and meant that wars were often fought for no better reason than boosting the personal reputation of the Emperor in fact Claudius' invasion of Britain is a good example of this. Hadrian building the wall on such an impressive scale (it was even whitewashed!)would have been to boost not just to the Empire but his own prestige. It seems very likely that he rejected simpler schemes in order to imprint his own monument at the very edge of the Roman empire, a symbol that would have impressed his power not just on the tribes outside but on his own subjects as well.
Who built the Wall?
The Wall was built by soldiers of the II Augustus, VI Victrix and XX Valeria Victrix Legions, with some help from soldiers of the British fleet.
Although it was built by the legions, it was not garrisoned by them but rather by the auxiliaries.
What happened after Hadrian?
Almost no sooner than the Wall was completed than Hadrian died and his successor abandoned Hadrian's wall to advanc again into Scotland. It's easy to imagine the comments from some of the legionnaires who had just expended years of sweat and toil on the Wall. For the next sixty years the position of Rome's northern border see-sawed back and forth, but following the death of the Emperor Severus it finally settled on Hadrian's Wall and remained there right until the end of Roman Britain. In the end Roman Britain succumbed to internal revolt and attacks from the sea. The sea defences along the Saxon shore became increasingly important, with the West coast coming under attack from raiders from Ireland. Hadrian's Wall was still manned right until the very last days of Roman Britain, with some of the forts even being occupied by the descendents of the garrisons after the collapse..