Between 360 and 366, Britain experienced a period of relative calm, with efforts seemingly focused on reinforcing its defences. However, in 366/7, the peace was disrupted as the Scots and Picts, possibly with assistance from other Germanic groups, launched a more coordinated and strategic attack than before, an event later referred to as the ‘barbarian conspiracy’. During this period, Valentinian held the title of Emperor of Rome, having ascended to the throne in 364. Reports reached Valentinian of a devastating attack by a coalition of Picts, Attacotti, and Scots, which resulted in the death of Nectaridus, the comes maritimi tractus, and the defeat of the dux Fullofaudes in Britain, plunging the region into chaos. This account is provided by the historian Ammianus Marcellinus.
It will be sufficient here to mention that at that time the Picts, who were divided into two nations, the Dicalidones and the Vecturiones, and likewise the Attacotti, a very warlike people, and the Scots were all roving over different parts of the country and committing great ravages. While the Franks and the Saxons who are on the frontiers of the Gauls were ravaging their country wherever they could effect an entrance by sea or land, plundering and burning, and murdering all the prisoners they could take
The Roman History, Book XXVII, By Ammianus Marcellinus
The Dicalidones, identified as the Caledonians, and the Saxons and Franks are noted for their raids along the coasts of Gaul and Britain. This period illustrates the close alliance between the Saxons and Franks, as evidenced by Frankish influences in Kent’s early settlements in Britain. Alarmed by these incursions, Valentinian embarked for Britain, initially dispatching Severus (comes domesticorum) to assess and address the issues. However, Severus’s efforts on the continent, and later in Amiens with Valentinian, did not yield success in stabilizing Britain. Consequently, Valentinian appointed Jovinus to Britain and elevated Severus to magister peditum, but to no avail. Thus, Theodosius the Elder was sent in 368 with legions including the Batavi, Heruli, Jovii, and Victores, landing at Richborough and advancing to London. His early campaigns in southern Britain reestablished some order. He later unified the fragmented troops in Britain, which had lost structure following Nectaridius and Fullofaudes’s defeats. During this period, Theodosius appointed Civilis as vicarius of the diocese, likely based in London, and Dulcitius as Dux Britanniarum, overseeing the frontier troops known as Litanei, likely stationed in York, as detailed by Ammianus in his account of Theodosius’ campaign in Britain.
But Theodosius, a general of very famous reputation, departed in high spirits from Augusta, which the ancients used to call Londinium, with an army which he had collected with great energy and skill; bringing a mighty aid to the embarrassed and disturbed fortunes of the Britons. His plan was to seek everywhere favourable situations for laying ambuscades for the barbarians; and to impose no duties on his troops of the performance of which he did not himself cheerfully set the example.
And in this way, while he performed the duties of a gallant soldier, and showed at the same time the prudence of an illustrious general, he routed and vanquished the various tribes in whom their past security had engendered an insolence which led them to attack the Roman territories: and he entirely restored the cities and the fortresses which through the manifold disasters of the time had been injured or destroyed, though they had been originally founded to secure the tranquillity of the country.
The Roman History, Book XXVII, By Ammianus Marcellinus
Around the year 369, Dulcitius faced a minor uprising incited by Valentinus, the brother-in-law of Maximinus, who was destined to later hold the position of Praetorian Prefect of Gaul. Valentinus found himself exiled to Britain due to an undisclosed offense he had committed in Rome, from which only the influence of the notorious Maximinus had spared him. Ammianus provides a direct account of Valentinus’s actions:
A certain man named Valentine, in Valeria of Pannonia, a man of a proud spirit, the brother-in-law of Maximin, that wicked and cruel deputy, who afterwards became prefect, having been banished to Britain for some grave crime, and being a restless and mischievous beast, was eager for any kind of resolution or mischief, began to plot with great insolence against Theodosius, whom he looked upon as the only person with power to resist his wicked enterprise.
But while both openly and privately taking many precautions, as his pride and covetousness increased, he began to tamper with the exiles and the soldiers, promising them rewards sufficient to tempt them as far at least as the circumstances and his enterprise would permit.
But when the time for putting his attempt into execution drew near, the duke, who had received from some trustworthy quarter information of what was going on, being always a man inclined to a bold line of conduct, and resolutely bent on chastising crimes when detected, seized Valentine with a few of his accomplices who were most deeply implicated, and handed them over to the general Dulcitius to be put to death. But at the same time conjecturing the future, through that knowledge of the soldiers in which he surpassed other men, he forbade the institution of any examination into the conspiracy generally, lest if the fear of such an investigation should affect many, fresh troubles might revive in the province.
The Roman History, Book XXVII, By Ammianus Marcellinus
Ammianus’s description reveals much about the situation in Britain, highlighting it as a common destination for exiles. Valentinus is mentioned as “tampering” with other exiles, a term which more accurately suggests he was conspiring with them. This implies a significant number of exiles were present in Britain, likely contributing to the region’s instability due to their dubious characters. Theodosius’s decision to not delve deeper into the conspiracy may suggest a desire to avoid reigniting the disturbances caused by Paulas Catena. Ammianus further narrates Theodosius’s efforts in Britain:
After this he turned his attention to make many necessary amendments, feeling wholly free from any danger in such attempts, since it was plain that all his enterprises were attended by a propitious fortune. So he restored cities and fortresses, as we have already mentioned, and established stations and outposts on our frontiers; and he so completely recovered the province which had yielded subjection to the enemy, that through his agency it was again brought under the authority of its legitimate ruler, and from that time forth was called Valentia, by desire of the emperor, as a memorial of his success.
The Areans, a class of men instituted in former times, and of whom we have already made some mention in recording the acts of Constans, had now gradually fallen into bad practices, for which he removed them from their stations; in fact they had been undeniably convicted of yielding to the temptation of the great rewards which were given and promised to them, so as to have continually betrayed to the barbarians what was done among us. For their business was to traverse vast districts, and report to our generals the warlike movements of the neighbouring nations.
In this manner the affairs which I have already mentioned, and others like them, having been settled, he was summoned to the court, and leaving the provinces in a state of exultation, like another Furius Camillus or Papirius Cursor, he was celebrated everywhere for his numerous and important victories. He was accompanied by a large crowd of well-wishers to the coast, and crossing over with a fair wind, arrived at the emperor’s camp, where he was received with joy and high praise, and appointed to succeed Valens Jovinus, who was commander of the cavalry.
The Roman History, Book XXVII, By Ammianus Marcellinus
Ammianus’s account sheds light on the enigmatic frontier scouts or spies known as the Areans or Areani. He reveals that these individuals, tasked with gathering intelligence on barbarians like the Picts or Scots, were compromised, having been bribed by those they were meant to surveil. Additionally, Ammianus notes that Theodosius departed from Britain leaving it in a stable and secure condition. However, a significant shift must have taken place soon after, as within a span of 13 years, a major revolt dramatically impacted Britain and the broader European landscape.
In 370, Valentinian took action to address the unrest in northern Gaul, targeting a group of Saxon raiders. After halting their plundering activities, the Saxons agreed to return home and provide soldiers for Valentinian’s forces. However, Valentinian betrayed their agreement, launching a surprise attack that led to the slaughter of the entire Saxon band. This act of treachery was a lesson that the Saxons would not forget, with repercussions that the Britons would come to experience in the years to follow.
Between 370 and 383, Britain enjoyed a period of relative tranquility, although it’s believed raiding resumed around 373/4. In response, Valentinian dispatched three Alamanni armies to bolster British defenses, led by kings Froamarius, Hortarius, and Bitherides, with Froamarius being granted the title of Tribune. Historical records suggest that during this era, identified by the consulship of ‘Gratian and Aquitias’ in 474 AD—a timeline associated with the rule of Vortigern—the Saxons arrived in Britain. This account, however, is chronologically misplaced, blending events from the 4th century with the later narratives of Vortigern and Ambrosius Aurelianus found in 5th-century historical recounts.
The presence of Maximinus as the Praetorian Prefect overseeing Gaul and Britain introduces further complexity, linking him to Milan’s Sanctus Ambrosius, suggesting entanglements of political and military narratives. The Alamanni forces, landing in Richborough (Rutupiae), were strategically dispersed across Britain: some reinforced Hadrian’s Wall in the north, others manned the The Saxon Shore Forts in Kent, and a contingent was sent to Wales to counter the Irish Scoti raids. This strategic reinforcement brought about a brief interlude of peace lasting until 383.