The British security situation deteriorated in the 360s. At the start of the decade we are told that `savage tribes of the Scots and Picts, who had broken the peace that had been agreed upon, were laying waste the regions near the frontiers’. Worse followed in 367, when a crisis known as the `barbarian conspiracy’ unfolded. Raids by Franks and Saxons targeting Gaul, and Picts, Attacotti, and Scots striking Britain brought devastation and suspicions of collusion. In Britain, one high-ranking Roman commander was slain and another, by the name of Fullofaudes, was `cut off by enemy ambush’. Fullofaudes was a dux, and therefore quite possibly the dux Britanniarum responsible for the Wall zone. His fate is not clear, but potentially he, too, was killed. Meanwhile, the attackers were `ranging widely and causing great devastation’ as far south as London, while scores of surviving Roman soldiers aggravated the catastrophe by deserting. In response, a force perhaps 2,000-strong under the command of Theodosius – the father of a future emperor with the same name – was dispatched from the Continent.
By the time Theodosius arrived, the enemy forces had splintered and were seeking out booty. To restore the situation, his soldiers adopted tactics once considered borderline banditry. They `secured beforehand the places suitable for ambushing the savages’, rather than – so far as we can tell – fighting setpiece battles. This approach proved provident and, after the danger had passed, Theodosius is credited with protecting `the frontiers with watch-posts and defence works’, and disbanding a group referred to as the areani. Its members reportedly ranged far and wide to gather information, making it likely they were a late incarnation of the Wall’s intelligence-gathering apparatus. If so, they expose an inherent danger of such outfits, as the areani were reportedly turned by the enemy and bribed into betraying Roman secrets. That assumes, of course, they were not simply singled out as a convenient scapegoat for a spectacular military catastrophe.
Although we do not know whether the 367 invaders directly targeted the Wall garrisons, or sought to bypass them, the killing of one senior Roman commander, and ambushing of another, emphasises that the attackers were powerful enough to inflict serious losses. There is no sign in the written sources that the Roman forces in Britain could have salvaged the situation without aid from overseas. If securing booty was the attackers’ principal aim, attempting to bypass the Wall garrisons would have an obvious appeal. Theodosius’ strengthening of the frontier defences may be relevant here. There is no sign of major upgrades to the Wall, but a chain of fortifications was raised along the north-east Yorkshire coast at around this time. These small installations are recognisable as a variant of a fortification type popular on the Continent and comprise stout stone towers set within high masonry ramparts boasting projecting bastions. Creating such a cordon could fit with the 367 conspirators simply sailing past the Wall and landing to its south. One complication is that the garrisons of these new coastal stations are unlikely to exceed about eighty soldiers, which would leave them wellsuited to counter small-scale incursions, but powerless to repulse a fullblown invasion. They do, though, perfectly match the implication of the western coastal forts at Maryport and Lancaster: it was securing the shore that warranted heightened protective measures during this era. Even so, this developing threat may be partially attributable to Hadrian’s Wall curtailing overland raiding so effectively it incentivised striking by sea.
Religious practices were also changing during the final decades of Roman Britain. At Corbridge, temples were torn down after 370, with elements reused in the road. Offerings at Coventina’s shrine seemingly cease sometime around 388, while broken fragments of superstructure were reportedly found in her well, which would fit with a deconsecration ceremony analogous to those sometimes found in fort headquarters buildings. This suppression of longstanding ritual sites can presumably be attributed to Christianity. With occasional exceptions, official tolerance for the religion had grown since Constantine’s victory at the Milvian bridge. In 391, an edict made sacrifice illegal and closed the temples. The degree to which Christianity penetrated the Wall communities remains unclear, and some see the military garrisons as bastions of the old gods. However, the evidence for a military uptake of Christianity seems reasonably good. A few overtly Christian objects have been found, perhaps most obviously those bearing the chi-rho emblem. This device superimposes the first two Greek letters for Christos and is sometimes set within a circle. On such occasions it evokes a six-spoke wheel, which would surely have elicited knowing smiles from any remining adherents of the Celtic sky god. Recent excavations at Maryport revealed a cluster of graves, some of which might have a Christian origin. These lay near an enigmatic concentration of large pits, many of which contained earlier altars reused as packing to support sizeable timber uprights for some sort of monumental structure erected during the twilight of Roman control. As this complex occupied the highest point of the local topography, it was presumably intended to be as visible as possible. Churches are suspected within South Shields, Housesteads, Vindolanda, and Birdoswald forts, while Christianstyle gravestones are known at Vindolanda and Maryport. Although these memorials probably date to the century or so after the end of Roman Britain, if Christianity was being practised by the descendants of fort garrisons, it seems reasonable to propose that the religion took root during the Roman era.
Magnus Maximus, an important commander in Britain and possibly another dux Britanniarum, is known to have been baptised in 383. He is also credited with successes against the Picts and Scots, but in 383 was proclaimed emperor by his troops. Maximus initially proved a proficient usurper, and successfully took Gaul and Spain, before invading Italy in 387, where he was captured and executed. It is likely that his continental adventures were powered in part by troops withdrawn from Britain. Thereafter, pressure on the island continued to mount. In around 398, reinforcements were sent against perils including a sea that `foamed with hostile oarsmen’. Less than a decade later, the army in Britain mutinied in 406 or 407, setting up a succession of usurpers as the situation on the Continent steadily deteriorated. In around 409, it was either invaders from beyond the Rhine frontier or perhaps even a desire to remove unwelcome military units brought in by the army that sounded the death knell for Roman Britain. Zosimus records that they `made it necessary for the inhabitants of Britain and some of the nations among the Celts to revolt from Roman rule and live on their own, no longer obedient to Roman laws. The Britons therefore took up arms, and braving danger for their own independence, freed the cities from the barbarians threatening [or billeted in] them’. While this passage implies that Roman Britain came to a neatly defined end, archaeology demonstrates the reality was less clear cut.
Rather than the Wall garrisons being withdrawn and the forts abandoned around 409, evidence for continued occupation is mounting. The classic sequence was teased out at Birdoswald during Tony Wilmott’s trailblazing 1987-1992 excavations. There, important changes to the two fort granaries began c. 350, when the subfloor spaces in the southern structure were filled in, while its northern counterpart collapsed at around this time. That the refurbishing of the southern granary marks a shift from storage to highstatus activity is implied by what is probably either a foundation or abandonment deposit: a gold earring, glass ring, and silver coin of 388-395, found near hearths. The last two continue the round objects theme, while the earring is hexagonal, but features a decorative scheme vaguely evocative of wheel spokes. Sometime afterwards, a new floor surface was laid on top, before the south granary was seemingly abandoned in favour of a timber building inserted into the shell of the northern granary. This was, in turn, superseded by a sizeable timber hall, which stood on postpads. Wilmott observed that the adapted granaries are explicable as venues where the unit commander could address his troops, while the final timber edifice resembles an early medieval chieftain’s feasting hall. The chronology fits this, with the adapted southern granary probably not abandoned until 420, the first quasi-timber structure lasting to perhaps 470, and the timber hall standing until 520 or later. This puts us over a century beyond the end date of Roman Britain. Crucially, though, no break in occupation was detected at the fort. Instead of marching away, the Roman garrison seemingly stayed put, gradually mutating from a regular army unit into an early medieval warband.
The centre cannot hold
The Wall changed immensely over the course of the 4th century. Failure to upgrade the military posts with cutting-edge new defences left them resembling relics from a bygone era. But inside, change was underway. Fort layouts designed to reinforce a hierarchy stretching all the way to the emperor, and hold storage and workshop facilities commensurate with sophisticated long-distance supply lines, were morphing into something new. Ruined or redundant monumental architecture could be quarried to patch humdrum but essential structures, such as defences and roads, or surrendered to industry, thereby helping to tackle the immense logistical challenges associated with becoming more self-sufficient. This shift surely involved local producers in the vicinity of forts supplying more goods for the military market, suggesting close links with rural communities. Currently, we can only see hints of this, but in the west, it is likely that some late Roman sites south of the Wall were successors to longstanding settlements with prehistoric origins. In the east, the endurance of Local Traditional Ware also supports a degree of continuity. A chronic reduction in overseas imports, and indeed products from southern Britain, robbed Wall life of a distinctive facet over the course of the 4th century. Yet transitioning to regional supply probably enabled soldiers to weather the early-5th-century turmoil. Rather than the end of Rome’s financial and material support forcing an abandonment of the forts, local suppliers offered a lifeline. In turn, the protection fort garrisons could extend provided an incentive for rural producers to nurture this relationship.
Severing links with Rome spelled fundamental change for existing power structures. No longer were unit commanders beholden to a distant dux, probably based in York, who was in turn just another cog in the imperial hierarchy. Instead, individual unit commanders would have had greater autonomy than ever before. Even this development, though, seemingly has its roots in the later 4th century. If the refurbishment of the southern granary at Birdoswald was designed to create a venue where a commander could address his men, it marked an important shift from the arrangement in previous centuries. Once, such gatherings occurred in the headquarters building, beside the unit shrine and the trappings of imperial power. The new arrangement at Birdoswald would have increased the focus on individual commanders. By this reading, the eventual shift to a timber feasting hall symbolises how regular military commanders gradually transformed into early medieval chieftains. The end of Roman authority over the Wall, then, was not accompanied by an evacuation of the heavily armed soldiers manning its forts. Instead they remained, to become part of the region’s future.