The Roman emperor Hadrian decided that a wall needed to be built to keep the marauding barbarians at bay for good. The Roman conquest of Britain was furthering its northern border, slowly now, and frustrations were high. A wall, it was decided, was needed.
Hadrian commissioned a 73-mile-long wall It from Wallsend on the River Tyne west to Bowness on the Solway Firth. Hadrian’s plan called for a hill 10 feet wide and 12 feet high, complete with a ditch on the Scottish side, a tower every one-third mile, and a fort (milecastle) every mile. Reality forced the Romans to build a fort every seven miles and reduce the dimensions of the Wall to 8 feet wide.
To the north of the Wall was a deep defensive ditch and to the south another ditch, the Vallum, flanked by mounds of earth. The Vallum, with crossing places at forts, was the Roman equivalent of the barbed-wire fence controlling civilian movement into modern military sites.
The Wall had the added benefit of creating little pockets of civilization around each fort. The soldiers had to be on duty most of the time, so they couldn’t very well live far away. Hence, camps and then settlements sprang up around the towers. Rome was leaving its mark on Britain in yet another way.
Perhaps the most important measure of the Wall, in Roman terms, was that it marked a boundary. About Hadrian’s time and a little later, with the reign of Marcus Aurelius, Roman emperors felt the need to stop the boundless expansion that had built the empire into the world’s greatest military and political machine.
In Europe, the emperors chose natural boundaries, like the River Danube, as a boundary of the Roman Empire. Hadrian’s Wall (and later the Antonine Wall) had the same purpose. In effect, the emperors were saying that they were through expanding and were eager to work to keep what they had gained. It was a fundamental change in thinking, one that enabled the Empire to survive for a few hundreds years longer than it might have otherwise.
Still, the danger to Rome itself was very real in the 400s, and the legions were called home from Britain. Romans left Britain in droves, but their buildings, bridges, walls, baths, roads, and customs survived.