It was a significant landmark both physically as well as psychologically – Physically it had the objective of protecting Roman Britain from the ruinous incursions of the northern barbarians of Caledonia (modern Scotland). Psychologically and socially it divided the barbarian tribes of the north from the Romanised population of the south, creating and reinforcing a distinct culture on the two sides which continues to this day – the Scottish clans of the north continue to this day whilst the tribes of southern England were homogenised into a single people.
The wall itself was a defence rampart built between 122AD and 128AD following the northern frontier of Roman Britain (Britannia): It stretched from coast to coast from the Solway firth at the west to the Tyne river in the East.
It was 120 kilometres long (approx. 75miles), 2.5-3 meters wide (8-10ft), 4.5 meters high (14-15 ft). There were fortified sections every mile, known as milecastles which were manned with approximately 60 men, and towers every third of a mile (two towers between milecastles) which held just a few men to act as watch and signalmen: either by lighting fires at night time or by running the short distance to the next tower like a relay race. Along the whole length of the wall there were 16 larger forts which could hold more significant garrisons of 500-1000 men each. These men could be displaced quickly to an area of larger attack by using the network of roads on the southern side of the wall. These larger castles also had gates fortified gates facing to the northern countryside.
The entire length was further reinforced by ditches on either side known as a “Vallum” with 2m high earth banks (approx 6 ft). Areas of particular danger might be further reinforced by having a false bottom on the vallum with stakes. The north side vallum was be approximately 9m wide (30ft) and 2.5m (9ft) deep.
The wall was initially built of wood and later made into stone. The turrets and castles were of stone and mortar whilst the wall sections were plastered over and painted white – clearly a fearsome structure which would have stood out for miles in the barren landscape – barren because all resources including stone and timber in the area would have been used to build the wall itself as well as the settlements which sprang up around it.
Construction technique varied throughout its length according to the terrain and materials readily available. The towers, set out at approximately every mile, were positioned so as to enable line-of-sight signalling from one to the next. Whilst the wall consisted of a variety of different construction techniques, the towers themselves were all made of hard stone and mortar. It is believed that its length was covered in plaster and painted. The entire lengths of the wall were further protected with earthwork ramparts and ditches known as the “vallum” which was dug after the wall itself had been completed and ran at varying distance from the wall itself, sometimes very close and at others, depending on the situation and terrain could be pretty far.
Today large portions of it are still visible, much more so than the parallel wall known as the Antonine wall further north (from which the Romans retreated).
Hadrian’s wall – part of the Limes
Hadrian’s wall is a wonderful example of the “limes” or “Limites” a word which finds its origins in the Etruscan aruspices (diviners) meaning the boundary between animal organs and entrails which they used for divining the future and to this day lies at the root of the word “limit”. At the time of Hadrian it stood for that series of fortifications built to strengthen the empire’s borders where natural barriers were insufficient to maintain a degree of control and preside the area. They were intended as a means of halting small scale incursions or of delaying larger attacks so that forces could be mustered in the affected area. Otherwise the intention was to allow free trade, economic growth and cultural exchange, benefitting both sides of the border. Internally the wall, like other limes (limites), was supported by a well developed network of the well known Roman roads to enable easy movement of troops and Roman legions.
As suggested above, Britain wasn’t the only province to deserve well structured fortifications. Other areas included northern Germany and perhaps more similar to Hadrian’s wall is the Anastasian wall (long walls of Thrace) built in the 5th century and abandoned in the 7th for being too long to garrison easily and expensive to maintain. Portions of it still remain of its original 55km (34miles). Other famous walls built by other cultures but with similar defence purpose include the great wall of china and more recently the maginot line of France in the second world war. It is interesting to note that none of these actually managed to keep any army “out” for any decent period of time.
So we should not imagine Hadrian’s wall as a barrier which was intended to be air-tight at all times; in fact the limes, including Hadrian’s wall, were actually intended more as a semi-permeable filter, enabling trade and inter-cultural mixing to continue, so long as it was peaceful. Hadrian’s wall is not to be considered purely from a military and engineering point of view but also for its social, economic and cultural aspects: the wall, like the empire’s “limes” was both physical and ideal at the same time, permitting populated areas to develop around it, thriving on the economy of the militia stationed at the wall and hence bringing intermarriage, families, manufacture and trade.
The wall was abandoned around 450AD, approximately when the Roman garrisons were recalled into Italy and the Roman empire fell and declined. Archaeological research suggests that the social, economic and cultural progress which had been made in the region, commonly referred to as “Romanisation”, fell back to its original state: the Britons left the populated centres and scattered, retreating from what was evidently a dangerous and undefended region, open to incursions from the northern tribes.