In AD 270 Aurelian became emperor, the Gallic Empire collapsed and Britain was once more subsumed into the Roman Empire. Aurelian, however, lasted only five years before his assassination and a period of turmoil led to the murder of his successors Tacitus and Florianus. Probus assumed power in AD 276 and over the next six years succeeded in giving the empire some stability, though not in Britain, where there was rebellion. Probus sent Victorinus, a Moorish officer, to sort out this problem. Zosimus said that Victorinus put down the rebellion by a clever trick but unfortunately does not elaborate on this. Probus also used Britain as a place to send captives including Burgundian and Vandal prisoners, intending that they should settle in the province; whether the intention was to get rid of them or, as Zosimus said, to use them to assist in putting down the rebellion is not clear. Probus lost the empire to Carus, his Praetorian Prefect, in AD 282 and Carus’s son Carinus took charge of the western part of the empire, assuming the titles of Britannicus Maximus and Germanicus Maximus.
Stability was not restored to the empire until Diocletian secured the imperial throne in AD 284. The next year he appointed Maximian as Caesar, his deputy with control over the western part of the empire. A year later, because of his successful rule in Gaul, Maximian was elevated to the position of joint emperor. A signet ring found in Britain portrayed their relationship. Diocletian was represented as Jupiter making decisions while Maximian was Hercules roaming the world to protect the empire against the forces of destruction. As Maximian had married Diocletian’s daughter this also indicated the link with Hercules as a son of Jupiter.
Maximian’s main task was to prevent pirate raids, which were increasingly occurring along the coasts of Britain and Gaul. This brought him into conflict with M. Aurelius Mausaeus Carausius, a Menapian from a region within modern Belgium. With his command covering the coasts of Belgica and Armorica and probably Britain, he was in charge of a fleet to drive off the pirates, mainly Franks and Saxons.
From his base at Boulogne, Carausius was successful in putting down piracy, so much so that he made himself a wealthy man. He was accused of letting pirates raid the coast, then capturing them when they left, and seizing their booty. This did not fit in with Maximian’s scheme of government for the west. He put a price on Carausius’s head whereupon Carausius, in either AD 286 or 287, sailed for Britain and declared himself emperor. Britain was now a province worth governing, as it was one of the most secure, prosperous and relatively peaceful in the empire. Why, therefore, it supported Carausius is not clear. He may have secured enough wealth to pay subsidies to troops to bring them over to his side or the troops in Britain may have become alienated towards, or indifferent to, the present imperial government. Carausius might have been an officer in a Roman legion for part of his career and was therefore known to the troops. Civilians, such as wealthy villa owners or merchants, may have resented paying taxes to Rome and taken an opportunity to rid themselves of this burden.
Maximian could not move against Carausius immediately as he was concerned with suppressing rebellions on the Rhine frontier. By 289, however, he had gathered a fleet but Carausius’s sea tactics ensured that he drove off the Roman fleet and Maximian appears to have been unable to secure a decisive victory. Instead, he put the best face he could on the matter and gave Carausius the title of Augustus. How far Carausius’s empire extended is uncertain. He had control of Britain and possibly the coastal areas of Gaul – coinage found in northern Gaul has his name stamped on it. The coins had been struck at several mints, one being in London and another at Rouen. He needed this coinage to pay his troops but the coins also show his imperial expectations. Early ones depict him clasping hands with a figure of Britannia and the legend ‘Expectate veni’ (Come, we have expected you). Others legitimate his authority with the words ‘Pax AUGGG’ (Peace of the three emperors).
Carausius’s empire was not destined to last. He was assassinated by Allectus, his financial officer, whose plot against him succeeded in AD 293, probably because Carausius had been weakened when Constantius, elevated by Maximian to the post of Caesar, seized Boulogne. This had loosened Carausius’s grip on the coast of Gaul. Constantius was now determined to seize back control in Britain, but he did not organize an attack until AD 296, possibly finding it difficult to raise sufficient ships until then. He divided his fleet into two separate parts. One, led by Constantius himself, sailed from Boulogne towards the Thames estuary; the other, under the command of the Praetorian prefect, Asclepiodotus, sailed from the Seine estuary. He was extremely lucky for a thick sea mist enabled him to avoid been seen by Allectus’s fleet, which was stationed off the Isle of Wight. He landed somewhere in the region of the Solent and, once he had embarked, ordered his men to burn the boats. He may have wished to prevent the enemy getting hold of them or perhaps he did not have enough men to leave some to guard the ships. Burning the boats also ensured that his men knew there was no way back.
Constantius’s fleet had been delayed by bad weather and only a few ships got through to land troops near Richborough. The greater danger, however, came from the troops of Asclepiodotus, who was advancing towards London. Allectus may not have been with his fleet but was somewhere in the south-east, for he was able to raise an army to meet the oncoming forces. The two armies met either in Hampshire or West Sussex. The battle resulted in the total defeat of Allectus and his subsequent death. The remnants of his forces retreated towards London, only to be trapped by those soldiers who had managed to land from Constantius’s ships. Allectus’s forces included Frankish soldiers who sacked the city before probably intending to return to their homes across the North Sea. They were slaughtered without mercy.
Constantius quickly sailed for Britain and was able to enter London in triumph. A bronze medallion, struck at Trier, records his entry. On one side is the head of Constantius with his titles. The other shows him riding into a walled city identified by the letters ‘LON’ for Londinium underneath. Before the wall kneels a figure with arms raised in supplication at his entry. His fleet, represented by a boat, has obviously sailed up the Thames. The inscription Redditor Lucis Aeternae (Restorer of the light that burns for ever) indicates the gratitude of the citizens.
Constantius immediately focused his attention on ensuring control over the army as well as securing the defences of the province, for Irish pirates were now menacing the west coast, the Picts were restless in the north and there were also pirate attacks on the eastern seaboard. A number of forts had already been constructed on the south-east and south coasts of Britain and these were reconditioned. These have been called the Saxon Shore forts but they were not built at the same time to form one coordinated defensive structure. Brancaster (Norfolk) and Reculver were built about AD 230. To these were added Burgh Castle (Norfolk), Walton Castle (Suffolk), Bradwell (Essex) and Lympne (Kent) in the 270s. At that time the small fort of Richborough was given more defensive walls and Dover was refortified. Carausius may have added Portchester but the fort of Pevensey (East Sussex) was not built until AD 370.
These were not forts in the strict military sense of housing units of troops trained to attack. Their stout walls and formidable turrets seem to have been designed for defence. Ballistae and catapults could be placed on these turrets. Soldiers and their families, who normally lived outside the forts, could take shelter in them. Their defences were against raiders coming across the North Sea, drawn by the wealth of the province. Yet raiders could easily slip between the forts and land anywhere along the undefended parts of the coast so it would have been necessary to construct a unified system of command that would ensure the defence of the whole eastern coast and its hinterland. It is also possible that a line of watchtowers was constructed along the Thames estuary, as one has been excavated at Shadwell. London would have been a great prize for seaborne raiders and early warning of their coming was essential. The western coastline was not left unprotected. Forts were built to guard the estuaries from Cardiff to Lancaster from raiders coming from Ireland and Scotland.
All these forts would have had to be used by the fleet. The Classis Britannica (the British fleet) already had bases at Dover and Richborough and after Carausius’s rule the latter became its chief base. Gaius Aufidius Pantera, prefect of the fleet, dedicated an altar to Neptune at Lympne, which suggests it was another base. Other forts would have provided facilities to moor and repair ships. It would have been easy to link the forts by sea and arrange patrols along the coast. There is no evidence of a road system linking one with another. In the south roads lead from Richborough, Dover, Reculver and Lympne to Canterbury, which has been suggested as being an off-duty station for the troops.
The northern frontier required extensive restoration, not because of destruction, but from decay. There had been no programme of repairs since Severus’s reign. It was time for intensive refurbishment and this was continued beyond Constantius’s visit. Some forts had their garrisons reduced; at Wallsend and Chesters buildings were demolished in one area of the fort and not rebuilt. In other forts, buildings were abandoned. It has been suggested that these open spaces were to house the tents of mobile forces that could move out quickly to put down uprisings. Constantius appeared to have ordered forts to reduce in size their principal buildings, as happened at Great Chesters and Housesteads. At Birdoswald the principia (headquarters), the praetorium (commander’s residence) and the baths needed extensive repair.
There were also differences in how the troops were housed. At some forts, such as Housesteads, rather than restore the barrack blocks, ‘chalets’ were built, laid out in rows, as if indicating that soldiers and their families could live there. Alternatively these may have housed the exploratores (scouts) whose duties took them into the Scottish lowlands. Restoration was also made to the south of Hadrian’s Wall at Lanchester, Binchester, Malton and Ilkley. In addition the walls of the fortress of York were rebuilt and the riverfront enhanced with a series of multangular towers, both for protection and to demonstrate the power of military might. This restoration took place over a long period and extended into the fourth century.
Constantius returned to Gaul in AD 297 to concentrate on the problems there. He took skilled men from Britain to rebuild part of the city of Autun in France, which may indicate that the towns in Britain had not suffered during Carausius’s rule. A panegyric on Constantius Caesar, compiled in AD 297, recorded that the Britons had greeted him, ‘with great joy after so many years of most wretched captivity … At last they were free, at last Romans, at last restored afresh by the true life of the empire.’ Allowing for the hyperbole it would seem that a new era had begun in Britain but to ensure that it would continue to be a prosperous province its defences had to be secured. That all was not yet secure is indicated by the return of Constantius in AD 305 to sort out further problems in the north.
Constantius had to leave Britain in AD 297 to deal with events in Gaul. Soon after Diocletian and Maximian abdicated and Constantius was proclaimed as Augustus with control over the west while Galerius ruled as Augustus in the east. One of their purposes was to separate the civil and the military administrations. The provincial governor was no longer a legate at the head of his troops but a civilian officer with total control of administration and the empire was split into dioceses under the control of vicarii (governors).
Renewed fighting in the north of Britain forced Constantius to return in AD 305 to lead a campaign against the Picts who had moved towards Hadrian’s Wall from their area of eastern Scotland. His son Constantine joined him but the details of their campaign are unclear. A panegyric to Constantius suggested that he penetrated into the furthest parts of Scotland, probably moving up the east coast. Other literary sources suggested that he moved north against the Picts and the Caledonii, and pottery evidence from this period found at Cramond on the Forth and Carpow on the Tay suggests that if he did move north he was making use of the fleet to bring supplies.
Either Constantius did not intend to complete the conquest of the north or he realized that he could not do this. He returned to York where, in AD 306, he died. According to Eutropius, his son Constantine, the offspring of a somewhat undistinguished marriage, was made emperor. Zosimus added a little more. He implied that Constantine had joined his father in Britain with the intention of seeking the empire. When Constantius died the next choice to succeed him as the western Augustus was Flavius Valerius Severus, Constantius’s Caesar. In Rome, the Praetorian Guard had already moved to declare Maximian’s son, Maxentius, as Augustus and this was supported by the Senate. The army in Britain, deciding that the son of Constantius was capable of ruling, had declared him to be emperor but for a while he was forced to accept the lesser rank of Caesar. Severus eventually was accepted as Augustus and Constantine became his official Caesar, which gave him some legitimacy. In AD 307 Maxentius moved against Severus and deposed him. Constantine gathered troops from Germany, Gaul and Britain, marched from Gaul across the Alps into Italy and decisively defeated Maxentius and his troops at the Battle of the Milvian Bridge in AD 312.
Constantine was, however, forced to share authority with Licinius as co-emperor. They divided the empire between them with Constantine basing himself in Milan not Rome. In AD 324 Constantine finally seized complete control and forced Licinius to commit suicide. Licinius had based himself at Byzantium on the Bosporus and in AD 330 Constantine moved his court there, proclaiming it to be the New Rome, and with great ceremony decreed that it should be called Constantinople.
Eusebius said that Constantine did return to Britain at least once in his reign but once ‘he had subjugated it’ he returned to Rome and concentrated his attention on other parts of the world. Coins produced at the London mint were struck with the legends Constantinus Aug (ustus) and Adventus Aug (the arrival of Augustus). The implication is that there were problems in the province but what they were is unclear. There may have been other visits. Coin evidence suggests that these were in AD 307, 312 and 314. He also declared himself Britannicus Maximus, suggesting that he had won a victory.
It may have been on one of these visits that he made changes to the government in Britain. About AD 312–14 Britain was split into four provinces, which are recorded in the Verona List. Two might have been named after the two Caesars – Maxima Caesariensis and Flavia Caesariensis; the other two were Britannia Prima and Britannia Secunda. Maxima was to the south-east with its capital as London. Prima was in south Wales and the south-western part of Britain. An inscription found at Cirencester, which formed the base of a Jupiter column, was dedicated by ‘Lucius Septimius … Governor of Britannia Prima’, which seems proof that Corinium was the capital. Flavia Caesariensis, possibly created from land in both the provinces of Britannia Inferior and Britannia Superior, covered the centre of Britain from north Wales to the Lincolnshire coast with its most important town of Lincoln as the capital. It may have included some of East Anglia in its territory but Maxima Caesariensis may have included the whole of that area. Britannia Secunda covered the northern area of Britain including the Wall with York, headquarters of Legio VI, as its capital.
Confirmation of these provinces is given by the report on the bishops attending the Council of Arles in AD 314. Eborius was Bishop of York in provincia Britannia. Restitutus was Bishop de civitate Londiniensi (London) in provincia suprascripta. Adelphius was bishop of civitate colonia Londiniensium, probably a mistake for Lindinensium as Lincoln was a colonia while London was not. He was accompanied by a priest and a deacon, which might indicate his superior status.
Collectively these provinces formed one of the twelve dioceses of the empire so that Britain was ruled by a vicarius. The British diocese was under the overall command of the Praetorian Prefect of Gaul who also controlled Transalpine Gaul and Spain. This effectively eliminated the direct access that governors of Britain had once had to the emperor. Equally, it increased the possibility of more taxation being imposed on the diocese, money that was needed to support the military forces.
Constantine also seems to have instigated other reforms such as improving the road system, judging by the number of milestones attributed to his reign and the following one. These would have helped communications between the forts. The army was reformed following the work which Diocletian had begun in two areas. Firstly, the officer class became more professional so that now they served their entire career in the army without alternating it with civilian office. Secondly, greater mobility was ensured with increased mobile field units (limitanei) being placed on the frontiers and their hinterlands. Evidence for this comes from the Notitia Dignatatum, which listed chains of commands and detailed civil and military officials of the empire and the units controlled by them. This is assumed to have been completed by AD 395 with corrections and alterations over the next thirty years. How far it was kept up to date is uncertain.
The forces in Britain were listed under three commands. The south and east were under the command of the Count of the Saxon Shore (Comes Litoris Saxonici) who obviously controlled the Saxon Shore forts and the areas between them. The northern area, which included Hadrian’s Wall, was under the control of the Duke of Britain (Dux Britanniarum) with his headquarters at York. Both of these commands had extensive forces on which they could call against attacks from the sea or from the north. Much later, probably on the command of Stilicho in AD 395, a new command was instituted, the Count of the Provinces of Britain (Comes Britannarium). These commands came into being over several years. Constantine had given the first two commands roving commissions by creating more cavalry and infantry regiments. The army had moved from being a garrison army to mobile units trained to move swiftly to counter any attack. These commands were not linked to the civil administration but covered wide areas across frontiers.
Constantine died in AD 337 and the empire again fragmented when his three sons divided it between them. Britain, Spain and Gaul were under the control of Constantine II, who invaded Italy in AD 340 to attack his brother Constans, who ruled Italy, Africa and the Illyrian provinces. Constantine II was defeated and killed at Aquileia. In spite of this warfare Britain seems to have remained relatively peaceful until about AD 342 when Libanius reported that Constans crossed to Britain in mid winter ‘with everything, cloudy, cold, and swell roused to total fury by the weather’. Julius Firmicus Maternus confirmed his ‘crossing the swelling, raging waves of Oceanus, in winter time, a deed unprecedented in the past, and not to be matched in the future’. As the Romans disliked crossing the sea during the winter storms the implication is that the revolt in Britain was serious; in fact, Libanius said that Constans did not announce his coming or give any warning. Possibly Constantine II had withdrawn troops from Britain in his bid for complete command of the empire and the northern tribes had taken the opportunity to revolt.