There is also the fact that there is a Vallum (a huge ditch and mound system that runs the length of the wall) on the Southern side of the Wall which goes against Bede’s idea of a protection from the North- surely a system such as this would suggest a threat from the south as well? Historians and archaeologist a like have argued the possibly purposes of this feature of the Wall. It is unknown if it was a second defensive structure, purely a marking place of the military zone for the people, or possibly even as some have argued a defended passage way in which messengers could run from fort to fort. The last idea is most unlikely, the ditches would have most likely have drained water from their surrounding and there is no evidence of any drainage or paving at the bottom of the ditch and therefore they would have had more of a swap in the bottom of it making running or marching nearly impossible. The fact that the Vallum doesn’t actually lead in to a fort would also mean a messenger would have had to climb up the side of the ditch to get in to the fort; overall making this an almost impossible scenario. However the idea of it being a further defensive structure is quite possible, a double mound and ditch system could act as a definite barrier, especially if it was guarded. Nevertheless there are again problems with this theory. If it was built as a second defence structure then it is unlike any other seen within the empire, with no fortifying towers or a rampart. If there was such a problem of getting manpower to have defences like these two, which it is greatly unlikely that there was, then why didn’t they simply dig a defensive ditch cheaply on the southern side of the Wall? This leaves the idea which I feel is most likely, that the Vallum acted as a marker for the Romans military zone. Then again there are things which could go against this, such as the fact that there is little evidence that there were guards or look out posts along it, although it is possible that the forts had a patrol that went along their section of the Vallum.
Another view that has been put forward on the purpose of Hadrian’s Wall is that it was built to stop tribes from the North and South uniting against the Romans. It is true that if this union between the tribes occurred the Romans would be in danger from any potential rebellions. Therefore it would have been tactical for the Romans to separate these two groups in such a way. The archaeology definitely supports such an idea; The wall was built solidly with many guarded gates to act almost as customs barriers making sure they knew what and who was coming through at all times. The Vallum is also a strong indication that supports the idea that any aggressors from the south would be prevented by the military zone southern ditches. The fact that there is some evidence that it was built after the Wall also indicates that the Brigantes tribe to the south of the Wall were possibly more of a threat than the Romans first anticipated, and therefore probably put up more of a resistance. Overall the idea of the wall being primarily a division zone, like that of the Walls found in the Rhine, is very possible. On the other hand the fact that soldiers at work on or beyond the Wall would be given leave to the South of it would suggest that this was the less hostile area, possibly due to the fact that this one appears to have been the most Romanised area of the two. The layout of the forts again also suggests this, with the majority of the forts important building being based on the southern side of the Wall.
The view that Hadrian’s Wall was a customs barrier used to tax and control all that came in to and left the Roman Empire, has also been put forward by historians and archaeologists. This is based primarily on the fact that there are such a large amount of gates in the wall. The double arched gates meant that there was little likelihood of anyone being able to push their way through before their goods were checked and the courtyards of the mile castles gave the Roman soldiers on guard duty an area to go through any goods. However this would surely not have raised such a massive amount of income, with many of the gates being quite a distance from any major trade routes, which would have made it worth the cost of setting up the Wall. Instead this proposition seems more likely to be a secondary purpose of the Roman Wall, with the income being raised by acting as a customs barrier being used to purely to pay for upkeep. The amount of the forts along the wall also questions the fact that it was primarily to act as a customs barrier as forts are only necessary to protect something which may be attacked. Written evidence from Vindolanda also indicates that supplies were transported along the Stanegate Road, which is in some paces quite a distance from the Wall again questioning the idea of it being built sorely as a customs and tax barrier.
The final view that has been supported by archaeologists and historians on the primary purpose of the Wall is that it was simply a strong frontier for the Roman Empire to mark the end of the Imperium. It acted not only as a defence for the land that the Romans had already taken, but was also an example of propaganda to portray the power and wealth of the Romans to the tribes they had taken over. This would have been apparently purely on the scale of the Wall. There is also evidence that it was once plastered and whitewashed, which would have made it a definitely imposing landmark. The fact that Hadrian didn’t intend to invade any more territories, which is highlighted by the literature of the time, indicates that the wall may have been for such a reason. It However seems almost a waste of money an resources to build such a massive feature purely to show off the wealth of the Roman empire in an area of it that would not be seen by many Roman born citizens.
Overall there are many different primary purposes that have been proposed by archaeologists and historians on the Walls function. However looking at the archaeological evidence it appears that it is more likely that the purpose of the Wall evolved over time, due to changes that occurred around it. For example although, it seem that the Wall wasn’t primarily a customs barrier, due to the original amount of forts that were built along it, making it appear to be much more military of nature, it could be that over time this could have been used as a secondary function to help fund the Roman occupation.
The wall also appears to have evolved to not purely be a defensive structure from the tribes from the North. This is suggested by the appearance of the Vallum, the south facing defensive structure. The fact that this was built some time after the wall suggests that there was a change in circumstances, with the southern tribes possibly rebelling more that the Romans initially expected them to. The Vallum is clearly built after the wall was finished; although it runs the length of the wall there are some places in which it is apparently diverted to go around areas of fort or key settlements, with no archaeological evidence that it was filled in for such places to be made it is a clear indication that the Vallum was made after the rest of the wall, suggesting that there must have been aggression from the south that the Romans felt a need to defend against.
Overall I think that the Wall played a very diverse role for the Romans. Initially it appears to have been made as both a defensive structure and a mark for the end of the Imperium. We can tell that the Romans felt that the initial threat was from the Northerners by the structure of the defences against them, with settlements linked to the forts appearing on the Southern side of the Wall and the main building within the fort also being places south of the Wall. It can presume that the Wall was initially to mark the end of the Empire by written ideas to show that Hadrian didn’t want to expand any further but instead appear to want to mark the boundaries of his empire. This is a decision that the Romans later went against, meaning that the Wall was for some time abandoned while another Wall was built further North. However after that project was abandoned Hadrian’s Wall appears to have been reoccupied again. Sources such as that of Aelius Spartanius, also indicate that the Wall was presumably to separate what was Roman from what wasn’t, also supporting the idea of the Wall being to mark the end of the Imperium. When trouble rose from the South the Vallum was constructed, which would explain why there are apparent defences from both the South and North, and the original settlements that would have been on the southern side of the Wall were now too established to move; so the Wall evolved to defend from both the tribes of the North and South leading to the idea that the Wall later helped to separate such tribes from rising against the Romans in control.
