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Ammianus Marcellinus- Res Gestae Divi Augustae
( ca AD 393)
Robert Vermaat

"The language of truth is unadorned and always simple."

The best contemporary source of information about Britain in the late fourth century is the late-imperial historian Ammianus Marcellinus. Though he was born in Antioch, Syria to a wealthy Syrian Greek family, Ammianus wrote in Latin. His major work, simply titled Res Gestae Divi Augustae, appeared after 390 or 391 and consisted originally of 31 books, of which 14-31 survive.

Ammianus became a member of the protectores domestici (the imperial bodyguard after the disbanding of the praetorian guard) at only 20 years of age. He served under the magister militium of the East in Mesopotamia. Though he travelled throughout the empire, most of his career was spent on actions against Sassanid Persia, including the fatal war with the emperor Julian in 363. By 383 he had settled in Rome, where he began writing down his experiences, and died after 393, probably in 397.

Ammianus set out to write a history like that of Tacitus, covering the period from Nerva (AD 96) to the death of Valens in 378. Unfortunately, the books that survive cover only the period 353-378, but luckily Britain plays a prominent role in that part. Though the principle focus of Res Gestae is the Persian campaign, in which he served as an officer under Constantinus II's general Ursicinus, where he witnessed the brutal events of the Persian capture of Amida in 359. He later served under Julian in the campaign that saw the Emperor killed and the army defeated near Nisibis in the summer of 363. Ammianus provides an in-depth sketch of the emperor Julian the Apostate, who commanded Britain and Gaul after being named Caesar in AD 355.


Ammianus is our major source of information about Britain as a chief source of grain during the reign of Julian, but also for the barbarica conspiratio of 367 and the fifth British province called Valentia:

Ammianus describes Britain as an important source of grain for Gaul. One large grain-producing area may have been Salisbury plain. Ammianus directly mentions ships that are arriving in recently recovered areas:

Res Gestae, Book XVIII, chapter 2-3
He decided, however, that before engaging in hostilities one thing above all imperatively demanded his attention. This was to enter and recover towns long since destroyed and abandoned, and repair their defences, also to build granaries in place of those which had been burnt, to store the corn regularly brought from Britain.

The significance of this reference is the word regularly, which gives us an indication what constituted the importance of Britain to the Roman empire. What Egypt was to Italy, Britain was to Gaul, much more so at the time of Julian, when the land was in dire straits. Britain was a haven of peace and quiet, which must have been very unusual, but also good for a stable economy.

360 - ‘Troubles in Britain’
Book 20 opens with an enigmatic reference to an action in mid-winter by Lupicinus, to react to an unspecified attack on Britain:

Res Gestae, Book XX, chapter 1
But in Britain, during Constantius’ tenth and Julian’s third year of consulship, the wild tribes of the Scots and the Picts broke their undertaking to keep peace, were causing destruction in those areas near the frontiers, and the provincials, exhausted by the repeated disasters they had already suffered, were caught in the grip of fear. The Caesar [Julian], who was wintering at Paris and was preoccupied by various fears, shrank from going in person as Constans had done before him to help his subjects across the Channel, in case he left the Gallic provinces without a ruler at a time when the Alamanni were bent on fierce war. He decided therefore to send Lupicinus, at that time master of cavalry…
…with him a force of Herulians and Batavians together with two units of Moesians, this commander reached Bononia
[Boulogne] in the depth of winter. He embarked his troops and reached Rutupiae [Richborough] with a favourable wind. From there he marched to Londinium [London], intending to take the field as soon as possible.

As Ammianus fails to return to the cause of these troubles, or how soon they were resolved, we are kept in the dark as to the severity of the events. The fact that a not inconsiderable amount of crack troops had to be engaged points to a serious incursion. Alternative views are that this was a local revolt, either by civilians or even by part of the military.

367 - ‘Barbarian conspiracy’
The so-called ‘Barbarian Conspiracy, in which many tribes at once attacked Britain in what is usually described as a concerted invasion by land and sea, is a landmark in the history of later Roman Britain. Ammianus is used as a contemporary source for this attack, but is what he writes really a conspiracy between four barbarian peoples? In most studies of the period, the events related by Ammianus are interpreted as a premeditated action, in which several barbarian invasions had made a pact to hit Britain at the same time: the barbarica conspiratio. In fact, Ammianus mentions several incidents, but without ever referring to one attack with those words. He starts with an incident around 364:

Res Gestae, Book XXVI, chapter 4
During this period [Valentinian had just chosen Valens as Augustus] practically the whole Roman world heard the trumpet-call of war, as savage peoples stirred themselves and raided the frontiers nearest to them. The Alamanni were ravaging Gaul and Raetia simultaneously; the Sarmatians and Quadi were devastating Pannonia; the Picts, Saxons, Scots [Irish] and Attacotti were bringing continual misery upon Britain; the Austoriani and other Moorish peoples were attacking Africa with more than usual violence; and predatory bands of Goths were plundering Thrace and Moesia.

Usually quoted as if this was the ‘conspiracy’, it is clear that this event took place a few years before 367. Even more so, quoted in full (which I have seen done in only very few occasions) it becomes equally clear that this ‘concerted attack’ is no more than a poetic recital of all enemies that have attacked Britain recently. For would we take this reference as evidence for a ‘conspiracy’, we would have to take into account that this ‘conspiracy’ involved a simultaneous attack by ALL enemies of the Roman empire!

This does not mean that something very serious did not happen in 367, an event that involved several raiding tribes. Ammianus refers to this disaster in full:

Res Gestae, Book XXVII, chapter 8
… Valentinian was shocked to receive the serious news that a concerted attack by the barbarians had reduced the province of Britain to the verge of ruin. Nectaridus, the count of the coastal region, had been killed, and the general Fullofaudes surprised and cut off. The emperor sent Severus, count of the household troops… Shortly afterwards Severus was recalled and Jovinus set out for the island, but sent an appeal for strong reinforcements…
It will suffice to say that at that time the Picts (the Dicaledones and the Verturiones), together with the warlike Attacotti and the Scots, were roving at large and causing great devastation. In addition the Franks and Saxons were losing no opportunity of raiding the parts of Gaul nearest to them by land and sea, plundering, burning, and putting to death their prisoners.

Though Ammianus mentions several peoples, and the word ‘concerted’ suggests an attack by more than one enemy, this is by no means proof of a ‘conspiracy’, which would involve a level of cooperation that never before, nor afterwards, seems to have been possible among the enemies of Britain. In fact, Ammianus mentions the Picts, Attacotti and Scots together, and then the Saxons with the Franks in the south, but attacking Gaul, not Britain. Only later does Theodosius encounter plunderers south of London, but these are not described as raiding barbarians (below). I believe that we should carry the ‘conspiracy’ of Picts, Scots and Saxons to the grave and leave it there.

The attacks were serious enough, however. After the emperor had sent Severus, then Jovinus, at last Theodosius the Elder (father of the later emperor), was sent to quell the revolt with the crack regiments of the Batavi, Heruli, Jovii and Victores, which landed at Richborough and marched to London:

Res Gestae, Book XXVII, chapter 8
Dividing his men into several detachments, he attacked the roving parties of freebooters, who were hampered by the weight of their spoils and driving before them prisoners and cattle…and then entered the town [London] in triumph.
This success encouraged Theodosius to undertake operations on a larger scale, but he waited for a time in some doubt about his safest course….Finally, he issued a proclamation promising immunity to deserters who returned to the colours and summoning many others who were dispersed in various places on furlough. This secured the return of the majority.

Res Gestae, Book XXVIII, chapter 3
Theodosius, bearer of a famous name, set out full of confidence from London, now called Augusta, with a force which he had re-formed with energy and skill. He forestalled the barbarians by seizing positions suitable for guerrilla warfare…routed and put to flight various tribes… He completely restored towns and forts which had suffered a series of calamities, but which were now strengthened to secure a long period of peace. … He restored cities and garrison towns, as I have said, and protected the borders with guard-posts and defence works.

Although these works are now interpreted as the start of adding stone walls to most British cities and towns, it is no longer thought that Theodosius actually rebuilt Hadrian's Wall. From this account we can deduce that the defences of Britain had suffered greatly during the time before 367, though we cannot be sure of the exact cause. It is clear that many soldiers had deserted from their units, at least London was in distress and Kent was full of plunderers. In the north, seemingly separate, the tribes had been roaming freely, though we have no clear evidence that the Wall had fallen, or even that the troubles in the south were directly related to the northern invasion. In any case, two expeditions failed before Theodosius, albeit cautiously, could regain the south, strengthen his forces and attack the barbarians in the north.

The northern invasion seems separate from the southern troubles, which are nowhere called an invasion, least of all by Saxons. It seems that there had been a breakdown of the social order, caused by or resulting in mass defections, which in turn led to (or were set off by) an invasion from the north. This remains unclear. A recent theory has explained the breakdown as caused by religious differences of Christian origin, combined with social unrest. It has even been suggested that Ammianus tried to glorify the emperor Theodosius by praising the latter’s father!

From at least 367 onwards, Britain seems to be divided into one extra province, Valentia. Though it was long enough in existence for it to be mentioned in the Notitia Dignitatum in the fifth century, we have no clue as to its geographical location. Ammianus ascribes the creation of this enigmatic fifth province, that has been located in several places since, to Theodosius:

Res Gestae, Book XXVIII, chapter 3
… He [Theodosius] restored cities and garrison towns, as I have said, and protected the borders with guard-posts and defence works. The recovery of a province which had fallen into the hands of the enemy was so complete that, to use his own words, it now had a legitimate governor, and the emperor, treating the matter as a minor triumph, decreed that henceforth it should be called Valentia.

Salway however suggested that this new province had been previously set up during the troubles. These last words, especially the 'minor' triumph (velut ovans), may point to the putting down of a rebellion, not to the rescue of an entire diocese from the clutches of the barbarians! In proposing a solution for this description and the enigmantic origin of Valentia in one attempt, Salway pointed to a very intriguing affair, which took place during or right after the 'liberation':

Res Gestae, Book XXVIII, chapter 3
One Valentinus from the Pannonian province of Valeria, a man of arrogant temper and a brother-in-law of Maximin. .had been banished to Britain for a serious offence. … After a good deal of open and clandestine reconnaissance his insatiable ambition led him to tamper with other exiles and such troops as he was in a position to secure by the bribes he promised.

But Theodosius got air of the plot and had the rebels killed, though hushing the matter up to forestall further unrest in the recently recovered province. Also, the stress that Britain now had a legitimate governor (implying that it did not have one before) and that the matter wasn't persued outside the execution of the major conspirators for fear of rousing the country (again?) is very telling. This may once again indicate that Britain in 367 did not suffer from a co-ordinated attack by the barbarians, but that it suffered from thorough de-stabilisation from an internal rebellion.

Though this proposal may explain the strange words in which Ammianus described the affair, they do not help in determining the geographical location of Valentia. Though Wales has been proposed, most guesses point to the north. Frere has proposed that it was Britannia Secunda that was split up (with Carlisle as its capital), because the title of the commander of the forces on Hadrian's Wall, the Dux Britanniarum (Duke of the Britains) would indicate a command that stretched over more than one province. Whatever its precise location, Valentia was a province that remained until the end of Roman Britain. The Notitia Dignitatum (drawn up c. 394 AD) mentioned it as one of the 5 British provinces:

Provinciae, Britanniae V:
Maxima Caesariensis
Britannia prima
Britannia secunda
Flauia Caesariensis.

The ranking of Valentia behind Maxima Caesariensis might also indicate it was not an unimportant province, either.


Ammianus is not a source for Vortigern, but very much so for the circumstances before his birth. It is clear that Vortigern’s parents were most likely to have been young during the troubles after the fall of Magnentius, the unrest of 360, and the 'disaster' of 367. It is also clear that this must have made an enormous impression on those alive, maybe giving rise to thoughts of departing from the Empire. However, the later fourth century was also a time of great riches, a time when the villas became ever larger and more prosperous. If the disaster of 360-7 had made a large impression on the minds of the Britons, the restoration must also have led to a time of great plenty.

The Classics Page A full (Latin) text can be found at: http://www.gmu.edu/departments/fld/CLASSICS/ammianus.html.


  • Ammianus Marcellinus: The Later Roman Empire (AD 354-378), ed. and trans.W. Hamilton, (Penguin Classics, St Ives 1986).*
  • Ammianus Marcellinus: Res Gestae Divi Augustae, (full Latin text at) http://www.gmu.edu/departments/fld/CLASSICS/ammianus.html.
  • Frere, Sheppard S. (1967): Britannia, a History of Roman Britain, (Chatham repr. 1992).*
  • Jones, Michael E. (1996): The End of Roman Britain, (Cornell).*
  • Salway, Peter (1993): The Oxford illustrated History of Britain, (Oxford).*
  • Snyder, Christopher A. (1998): An Age of Tyrants, Britain and Britons AD 400-600, (Stroud).*

VortigernStudies is copyright Robert Vermaat 1999-2007. All rights reserved