Hadrian's Wall is the most famous border of the Roman Empire. Located in the north of England, very close to the border with Scotland, it crosses the island of Great Britain from east to west, from the North Sea to the Irish Sea. Absolute symbol of the Roman conquest, the last frontier of the Empire, it unrolls its vestiges in the middle of the moors swept by the winds. Today a kingdom of sheep, the region was in antiquity populated by soldiers. Alone in a tower or with a few brothers in arms in a fort, they watched the north and an improbable attack by invaders from the other side of the world. A thousand leagues from the Mediterranean, frozen with cold and overwhelmed by the daily or almost daily rains, their destiny has inspired songs and poems, well helped by the nostalgia inspired by this solitary wall. Not insensitive to this imagination, I myself wanted to go see it, and you know me, I took my camera. Southern Britain, known to the Romans as Britannia, was conquered in the first century AD. In AD 43, Emperor Claudius sent four legions across the Channel. Many episodes of revolts and bloody repressions later, the Roman armies begin the conquest of Scotland. But while the victory is almost achieved, General Agricola is recalled to Rome and his armies fall back to the south. They settle on a line narrow enough to be effectively defended, which will become the wall. This is where Hadrian comes in. After the great conquests of his predecessor Trajan, Hadrian inaugurated a more defensive era. The Roman Empire is at its height, it is more than 5 million square kilometers and continuing the conquests proves difficult. Hadrian therefore actively invested in diplomacy with the barbarian peoples to secure the confines of the Empire and he even abandoned some distant provinces such as Mesopotamia. Above all, he launched major works on the most exposed sections of the borders. After Africa and Germany, he went to the island of Brittany. It was there that he ordered the construction of a completely new device that will keep his name: a 117 kilometer line of fortifications between the bottom of the Gulf of Solway and the mouth of the Tyne. Nowhere else will Rome erect such a defensive device. Hadrian, who himself lived alongside the army, no doubt took pity on his men, exposed to the incessant ambushes of rebellious tribesmen who came and went freely. We must therefore act quickly. In its first phase, the wall was built in clods of earth cut with a spade and piled up by the legionnaires, who were requisitioned for the occasion. They are used to it, masonry or earthworks are part of the job. At the front of the wall, the ditch from which the earth is extracted also forms a major obstacle. Completed in a very short time, this first construction is not final. In a second phase, the wall is consolidated. In Roman fashion, a stone facing is applied to a work of opus caementicium, stones and rubble indiscriminately poured into the mortar. The foundations of the wall show a thickness of three meters but the elevation was undoubtedly narrower. At the top, imagine a small patrol path and perhaps a wooden parapet with battlements. This fortification can pass for an admission of weakness of Rome, barricading itself because not having been able to overcome, however this massive wall, continuous and well guarded, addressed all the same to the barbarians a very explicit warning. With its 4 or 5 meters in height and its whitewashed stones , the rampart contrasted sharply with the landscape of the British moors. Especially since the wall was completed by forts called milecastles. Regularly spaced a thousand paces, or 1481 meters, they are Roman rationality in its purest expression. In all, there are therefore 80 small castles, each of which accommodated a few dozen men. Here one of them, the milecastle n°39 still delivers vestiges of the internal buildings, warehouses and houses which sheltered during several centuries the soldiers of the wall. Auxiliary soldiers of a lower status than the legionnaires since they were not Roman citizens, they were also less paid and less equipped than their comrades in arms, stationed further south. Originally from Spain and Gaul in particular, they were increasingly recruited locally with the Romanization of the island. In addition to the maintenance work on the wall, they also take care of the cows and herds of sheep which provide them with the meat and wool they need to face the winter. Between two forts like this, two watchtowers were erected and offered an unobstructed view in all directions. In parallel, a paved road followed the device and allowed to maneuver troops quickly. At the back of the road, on the Roman side, another ditch was dug, the vallum. Three meters deep and six wide, it was designed to slow down marauders trying to leave in the other direction, or to protect themselves from the Brigantes tribe, settled in Roman territory, but whose loyalty was very relative. You can still see the remnants of this wide ditch here near Cawburn. Finally, a network of larger forts, spaced about eleven kilometers apart, reinforced the whole. They were to accommodate the strength of a cohort, approximately 500 men. Some of them are still well preserved, like here, that of Vindolanda. Equipped with granaries, ovens, an infirmary, craft workshops, stables, small temples and a headquarters, they reveal in detail the daily life of the soldiers of the wall. Outside the camp, the inhabitants of the surrounding area also built shops, taverns and brothels, to extort from the soldiers the few deniers of their pay. Small towns are thus born and veterans who have taken wives on the spot often build their house near the wall where they have lived for years. In Housesteads, the fort is directly stuck to the wall, at the top of a hill. It offers stunning views over the moor to the north. Archaeologists have unearthed vast stables there, essential for rapid intervention in the event of an attack on the wall. The remarkably well-preserved latrines are located at the southeast corner of the camp, away from the accommodation. Chester Fort is strategically positioned on the North Tyne River. The east gate opened directly onto a stone bridge, again controlling circulation. The commandant's house with its vast paved portico was installed in the very center of the camp. Around, the soldiers' quarters are much narrower. With its continuous rampart, garrisons and fortresses, Hadrian's Wall was an exceptional defensive device, in the literal sense. It is a unique case. It was the geographical reality of Britain, with its easily exploitable natural obstacles, that prompted such a response to the Roman conqueror. Elsewhere, the border provinces of the empire are equipped with legions but they are not fortified at this point. It is in any case unthinkable to build, monitor and maintain a comparable device over several thousand kilometres. We therefore most often rely on rivers, mountains or deserts to constitute natural ramparts. The objective of such a military presence on Hadrian's Wall, however, was not to erect an impassable barrier, it is not realistic. A determined enemy troop could easily find a poorly guarded place and cross the border. The goal sought by Hadrian was much more to control checkpoints, and to collect customs duties. We see it in the milecastles since a door of the castle opens to the north and allows passage, under military control. Textual or archaeological sources , moreover, reveal only a few traces of attacks on the wall itself. On the contrary, we see Roman objects spreading among the border peoples to the north. Everywhere on the borders of the empire, the presence of soldiers, having a good purchasing power and receiving supplies from the State, stimulates the local economy. Hadrian's Wall is no exception. Preventing a hostile army from crossing the border of the Empire being impossible anyway, the most important thing is to stop it quickly. Fires lit on the towers arranged along the road to Eboracum, today the city of York, made it possible to call in reinforcements from the Sixth Legion which was stationed there, a hundred kilometers further south. The best asset for the defense of the Empire ultimately remains to maintain a road network in good condition. For Rome, the border is above all the road. It is for this reason that it was called limes. This term, which gave our “limit”, is often used to designate the whole fortification system, but in reality, it originally designates the path that borders a field and which acts as a demarcation on the cadastre. In military vocabulary, the limes is the road for patrols, which also symbolizes the border between the barbarian and civilized world. When Hadrian died in 138 AD, his successor Antoninus prepared an expedition to the north of the island to occupy an even shorter line of defense between the mouth of the Clyde and the Forth. , near Glasgow and Edinburgh. A new wall is therefore built in earth and wood in 142, it is the Antonine wall. But too close to the Scottish Highlands, this new border exposes the Roman army to relentless attacks from local tribes. Only twelve years after its construction, the new rampart was abandoned, the army fell back, back to Hadrian's Wall. The following centuries are marked by revolts and civil wars, and Britannia is no longer a priority for Rome. However, the Empire clings. The emperors and generals who visited Hadrian's Wall found that it was falling to pieces and repeatedly launched renovations: Septimius Severus in 208, Constantius Chlorus in 296, and finally Theodosius in 368. But this restoration of the wall is the last. In 410, Emperor Honorius decided purely and simply to abandon the island of Britain. The Visigoths have just plundered Rome, and the Breton legions are called back to the continent. Too bad for Britannia. From one day to the next, the balances are no longer paid and supplies no longer arrive. One can imagine the dismay of those who dedicated their lives to Rome and sacrificed several decades of their lives to patrol the wall in solitude and freezing rain. Suddenly dismissed by an imperial missive, the soldiers must leave their garrisons and return to civilian life. Having known nothing other than military life, some enlist as mercenaries. Foreigners try to return to their provinces of origin and others stay nearby to attempt a reconversion. The agglomerations that have developed on the edge of the camps therefore persist for a time. Craftsmen and merchants have been established there for a long time, but without the presence of the army, the outlets disappear. The fortifications are falling apart again, this time definitely. The ditches are filled in and the stones are reused to build churches or houses. It's the end of Hadrian's Wall. If they packed up 1,600 years ago, the Romans still left a bit of the Mediterranean in the landscape. At the foot of the wall, among the Galloway cows with their thick fleece, a sycamore maple grows today. Solitary watchman, lost far from the continent, he is like a memory of this ancient presence.
