17

THE CHILDREN OF CONSTANTINE

Constantine had died in May 337. Until 9 September, he remained technically the ruling augustus, for none of his sons or generals proclaimed themselves augustus. What his sons did, they did as caesars. Constantine’s will was concealed by the praepositus sacri cubiculi, head of the imperial household. This was Eusebius, a eunuch who was a longstanding and loyal partisan of the middle son, Constantius II. That meant in turn that Constantius more than any of his brothers could arrange the empire’s affairs without reference to others. The power of the late emperor’s sons was consolidated by the massacre of male kinsmen who were not, like them, born to Constantine and Fausta: Constantine’s half-brothers Julius Constantius and Flavius Dalmatius died, as did the latter’s sons Dalmatius and Hannibalianus. Gallus and Julian, sons of Julius Constantius by different mothers survived, but survival did not imply trust: both were confined under close house arrest in the imperial palace at Nicomedia, where they were to grow up under the watchful eye of the local bishop Eusebius, who had been with Constantine on his deathbed. There, Julian was trained by a eunuch grammarian named Mardonius (as possibly was Gallus as well) who inspired in the boy a love of the Classical Greek literature and mythology that would later blossom into an extraordinary conversion to traditional paganism.

Constantius II, Constantine’s middle son by Fausta, was the main instigator of the great massacre, and in its aftermath he proved himself almost as adept at controlling a historical narrative as his father had been. Eusebius of Caesarea, who wrote a Life of his hero Constantine in 338, utterly effaces Dalmatius and Hannibalianus from the historical record, along with Constantine’s half-brothers, going so far as to assert that Constantine had willed that his empire be ruled by his sons alone. The one major source even to mention the massacre is Aurelius Victor, who wrote his De Caesaribus, a heavily abbreviated history of the Roman emperors, while Constantius II was still alive. It spouts what must have been the official line: the army had insisted that only Constantine’s children should rule and forced on them the execution of Dalmatius. Better still, and in typically Constantinian fashion, it suggests that Dalmatius and Hannibalianus had plotted against Constantine before his death and might even have been responsible for it. The truth has only been worked out by meticulous study of the coinage sequence. Constantius II had acted alone in ordering the massacre, even if he had his brothers’ tacit approval, and after the three were declared augusti publicly in early September, they met at Viminacium in Moesia, in territory that would have gone to Dalmatius under their father’s 335 settlement, to negotiate terms on which they could coexist. At least one eastern garrison had mutinied in response to the dynastic murders and Armenia was in open revolt after the loss of its putative king Hannibalianus, so the stability of the new arrangement remained in some doubt.

And of course the brothers could not trust one another. As such, neither Constantinus, Constantius nor Constans took the consulship of 338, handing it instead to Flavius Ursus and Flavius Polemius, two senior generals whose acquiescence in the coup helped calm the army. But that was symbolic, and real power would be kept in the family. Constantinus (or Constantine II, as he is sometimes known, especially among coin collectors) was the eldest, and he retained the western portion of the empire that had been assigned to him under the original Constantinian dispensation of 335. The youngest, Constans, had not yet reached his majority, but divided the share of Dalmatius with Constantius II, giving Thrace to the latter, while himself taking the dioceses of Pannonia, Macedonia and Dacia, the latter two having been split by Constantine out of the tetrarchic diocese of Moesia. The main beneficiary of this change was Constantius II, whose share brought with it both Constantine’s new foundation at Constantinople and the whole of the east. His first action as emperor was to execute Flavius Ablabius, one of the main architects of Constantinian government, and praetorian prefect at the time of the old emperor’s death in May 337. Ablabius, a Christian and an intimate of Constantine, had been prudent enough to retire to his huge estates in Bithynia when the emperor died, but – perhaps because of his proximity to the captive princes Gallus and Julian at Nicomedia, perhaps because of his own well-established power base – lying low was not enough. Ablabius’s associates, and many others who might have favoured the settlement of 335 rather than that of Constantius II and his brothers, were purged as well.

Yet Constantius’s ruthlessness was not enough to keep the peace. He may personally have been quite secure, but in the west the relationship of Constantinus and Constans was parlous, the elder brother attempting to treat young Constans more like a caesar than as an augustus in his own right and sending directives to Constans’ officials in a way he dared not do to Constantius’s. Obscure though events are, the regimes at Trier and Mediolanum were at odds from the moment the fraternal conference at Viminacium concluded. By 340, things had got so bad that Constantinus invaded Italy, on some pretext unknown to us. Constans’ generals met the invaders at Aquileia and Constantinus was killed on the battlefield. There were now just two emperors, with Constantius very much the senior partner, even though Constans held a larger, and rather more secure, part of the empire.

For us, the story of the next decade is more one of ecclesiastical politics than might be imagined, though whether it was experienced as such by those who lived through it is another matter. Our perspective is forced on us by the sources, which record next to nothing about secular history until the dawning of the 350s. Thus the political history can be sketched very briefly indeed. The death of Constantinus left his western regime intact so that Constans, who was completely unknown to the Gallic establishment, had little choice but to work with Constantinus’s advisers and supporters. He seems to have made every effort to do so, leaving Italy and the Balkans behind for the better part of three years, residing at Trier between 340 and 342, accompanying the army on at least two Frankish campaigns and touring the British armies. He divided the next two years between Trier and the Balkans, and then settled down where he was most comfortable, at Sirmium – a decision that exacerbated the existing rivalry between the Gallic and Balkan high commands. That particular rivalry would repeatedly have fatal consequences during the fourth century but, in the short term, Constans had to be in the Balkans to manage a fraught relationship with the regime of his brother Constantius.

The latter, after the dynastic slaughter of 337, faced a problem in Persia. Shapur had understood the scale of Constantine’s bellicose intentions in 337 and was prepared to meet the army mustering at Antioch when Constantine died. Rather than await the Roman invasion, Shapur struck preemptively, attacking the fortified citadel of Nisibis in Mesopotamia. As would happen again more than once, the Persian army got bogged down in the siege of Nisibis, failing to take it by storm and withdrawing back to Persian territory early in 338. Rather than press the advantage, Constantius merely sent an army into Armenia to put down the revolt there and install a compliant Arsacid on the throne. He also concluded an alliance with some of the Arab tribes in the desert between Roman and Persian territory. Feints and border skirmishes followed on both sides – one source suggests that there were nine battles between Constantius and Shapur, two of them with the emperor himself commanding – until in 344 the Romans suffered terrible losses at Singara, where one of Shapur’s sons was also killed. Deadly as the battle had been, it was not decisive, and the eastern provinces braced themselves for another Persian invasion. Indeed, fear of Shapur was the excuse used by many eastern bishops to stay away from a major church council, at Serdica in the Balkans, in 342. It was this council of Serdica that caused the first major crisis between the imperial brothers.

Religious controversy forms the largest part of what we know about the 340s, and that is appropriate inasmuch as Constantius II was personally very interested in theological questions. The difficulty both he and Constans faced was the failure of the Nicene settlement to stick: Arius had died in exile (on the toilet, of haemorrhagic diarrhoea, according to hostile witnesses), but bishops sympathetic to his formulation of the relationship between God the father and God the son reacted by working out a new terminology to counter the objections to Arius’s original teaching as aired at Nicaea – that father and son were ‘alike’ or similar in all things, but not identical. These ‘homoians’, as they were labelled by their detractors, found a leader in Eusebius of Nicomedia, the favourite of Constantine and bishop of a Bithynian polis historically locked in rivalry with neighbouring Nicaea. Constantine, in his advancing years, clearly supported the homoian formulation, and it was, as we saw, Eusebius of Nicomedia who baptised him on his deathbed in 337. Nicene extremists, most notably the bishop of Alexandria, Athanasius, who had succeeded his patron Alexander in 328, argued that the creed of Eusebius and his fellow bishops was nothing more than Arianism in disguise, incompatible with the true Nicene faith – only total likeness of substance in the godhead, the homoousianism of 325, was acceptable.

One of the last religious controversies in which Constantine had been engaged was the trial and exile of Athanasius in 335. The Alexandrian bishop, a political operator of great skill, seized the opportunity presented by Constantine’s death to return to Alexandria, where he openly challenged the rights of the incumbent bishop, Gregory of Cappadocia, who had been installed on the late emperor’s orders upon Athanasius’s exile. The city of Alexandria was of course notorious for its public disorders and had been for centuries, but Athanasius positively encouraged his supporters to riot and attack their opponents. It is a reminder of how easily, thanks to Constantine’s open endorsement of Christianity, theological disagreements could be used as excuses for public violence; indeed, there is a level at which the ‘sacred violence’ of late antiquity was a sort of hooliganism that might well have found outlet in gangsterism or banditry, but was instead legitimised by religious rhetoric. In the fighting of 337, Athanasius and his supporters won, but the bishop had failed to reckon with attitudes of the new emperor, a character as bloody-minded as the Alexandrian bishop himself.

Constantius, more than his father, was a convinced homoian and he would expend a great deal of energy during his reign in trying to find some variation of a homoian formula that could unify all the bishops of the empire. Over the course of his long reign, he called putatively universal and ecumenically binding councils half a dozen times: at Antioch (341), Serdica (342), Sirmium (351), Arelate (353), Mediolanum (355), Ariminum and Seleucia (359) and Constantinople (360). In all of these, he personally intervened in the drafting of creeds he intended to be universally acceptable, and therefore universally enforced. He failed in this ambition every time, in part because the theological differences he was trying to paper over were too wide, in part because partisan politics was deeply entrenched in the post-Nicene episcopate. Yet part of the blame also lay with Constantius, who persecuted the extreme Nicene party without let-up and freely exiled bishops who refused to conform to his homoian line. One of his earliest moves was to replace Paul, the Nicene bishop of Constantinople, with Eusebius of Nicomedia. Paul was exiled to Pontus, but his arrest by imperial troops led to rioting in the streets, during which an imperial officer named Hermogenes was lynched. Constantius then turned on Athanasius.

The latter had been condemned by a council of hostile bishops called in Egypt after his return from exile in 337. When Athanasius refused to accept this local council’s condemnation, his rivals appealed to the emperor, who agreed to meet with Athanasius in Caesarea. The Alexandrian bishop had mustered powerful support, not just from Greek sympathisers but also in the Latin west, a manoeuvre that would have fateful consequences for imperial politics. Constantius, however, remained hostile and summoned a council to meet at Antioch and judge the case: on 16 April 339, Athanasius was again condemned and sent into exile, this time at the court of Constans. The western emperor was disinclined to support his brother in religious matters and consistently backed the Nicene party throughout his reign. The brothers agreed to sponsor a council at Serdica in 342, not just to deal with Athanasius but to consider the trinitarian language of Nicaea yet again. Constans, however, permitted intransigently Nicene Latin bishops, led by the now ancient Hosius of Corduba, to head the western delegation. They refused even to be seated alongside the eastern bishops, and the council was a total failure. In its aftermath, Constans sent a menacing letter to his brother, demanding that he allow exiled bishops – for which read Athanasius of Alexandria – to return to their sees. Constantius refused, and in retaliation each emperor appointed different consuls for 344.

In 345, Constantius proclaimed a joint imperial consulship with Constans, with himself as senior partner, but the latter failed to recognise it until late summer, when Athanasius was allowed to return to Alexandria: only then, on 21 October, was the joint consulship proclaimed in the west as well as the east. What lay behind Constantius’s change of heart is uncertain, but it may be that the endless fighting on the Persian frontier had left him with no stomach for a civil war. Patching up the situation with his brother would at least allow him to concentrate safely on Persia. Constans did nothing to help his brother pursue the Persian conflict, even though he commanded a far larger military establishment that could have accomplished a great deal on the eastern front. Instead, he continued to reside at Sirmium, ready for a potential confrontation. It was in these years, with Constans firmly based in the Balkans and Constantius on the eastern front, that a major administrative transition took place: where formerly the praetorian prefects accompanied the emperor, so that their prefectures were not fixed geographically, there now developed a system of regional prefects, who acted with executive authority in the emperor’s stead.

This change was politically important, in part because it played a role in the downfall of Constans. The military and civilian establishments in Gaul had been catered to throughout the reigns of Constantine and Constantinus with a resident augustus or caesar. But with Constans far away in the Balkans, and clearly favourable to its rival high command, the Gallic establishment felt both neglected and resentful. Fabius Titianus, praetorian prefect of Gaul since 341 and thus one of the longest-serving holders of that office, formed the centre of a conspiracy that allied the civilian and military hierarchies of the western provinces against those of the Balkans. The conspirators included the senior western financial officer, the comes rerum privatarum Marcellinus, and a general high up in the Gallic field army, Flavius Magnentius, who would lead the planned coup. Titianus, whose long tenure speaks to the trust in which he was held, may have decided to go along with the conspirators out of enmity with Constans’s magister officiorum Eugenius, who was, like Titianus, a long-serving minister but one firmly tied to the Danubian high command.

Towards the end of 349, Constans returned to Gaul, and it was then that the trap was sprung. On 18 January 350, while the emperor was off on a hunting trip, Magnentius was proclaimed emperor at a birthday party for the son of Marcellinus, to which he had arrived dressed in the imperial purple. Rather than confronting the threat, Constans tried to escape, but was tracked down by a comes named Gaiso towards the end of January and executed – the officer’s reward would be a joint consulship with his emperor Magnentius in 351. Constans’s body, some scholars believe, was recovered by loyalists and buried in an elaborate mausoleum at Centcelles, over the Pyrenees from the Gallic village of Helena where he had been killed.

There were loyalists elsewhere as well, and a distant cousin of the imperial brothers was proclaimed at Rome. This Roman coup was sponsored by Eutropia, a half-sister of Constantine who had survived the massacre of her male relatives. Her son, Julius Nepotianus, was clad in the purple and immediately began to mint coins in his own name. But his position was weak. Constantine’s reforms had left no meaningful military force in Rome, and no praetorian guard who might sponsor a new emperor. Nepotianus had to rely upon a makeshift force of gladiators to back him and, without a field army, he was completely helpless when Magnentius sent troops over the Alps to suppress him. He and his supporters were massacred, though Eutropia was allowed to live. And that was not the only usurpation. Vetranio, Constans’s magister militum in Moesia, also seized the purple in response to the Gallic coup.

The episode is baffling, and the sources almost certainly conceal the truth. We are told that Constantia, the sister of Constantius and Constans, encouraged Vetranio to take the purple when she learned of her brother’s death and Magnentius’s usurpation. Vetranio was an old and trusted associate of the family, the brother of Julius Constantius’s first wife and thus a distant relative by marriage; he would protect the dynasty’s interests, and he won the approval of Constans’s loyal prefect of Illyricum, Vulcacius Rufinus. Rufinus personally carried a letter from Constantia to the eastern citadel of Edessa, where Constantius was in the midst of a Persian campaign. Constantius, as senior augustus, accepted Vetranio as his colleague and sent him a diadem. Or so we are told. It may all have happened, or the story may disguise a coup by the Balkan high command. We shall never know, but from Constantius’s perspective, it was better if the field armies of Gaul and the Balkans served different masters than if Magnentius took control of Illyricum as well as Gaul and Italy.

The western usurper appointed his brother Decentius as caesar and left him to oversee the Rhine frontier while he himself took control of the government in Italy. Constantius could do nothing, for he found himself confronted with yet another Persian invasion, led by Shapur himself. Like previous ones, it foundered on a siege of Nisibis, which held out for four months before Shapur retreated. Only then could Constantius begin to consider the murky situation in the Balkans and a usurpation that clearly had the support of a wide variety of western elites. In 350, Constantius led his field army back to Europe and Vetranio went to meet him at Serdica in a clear gesture of reconciliation. Whatever had spurred the usurpation, and whatever was now worked out between them, the two appeared together at Naissus on 25 December 350, a day that was not yet given special significance as Christmas Day. Both the Balkan and eastern field armies were drawn up in full parade for the occasion and, as Constantius began to address the assembled soldiery, they began to chant for Vetranio’s abdication. That was according to a pre-arranged plan and the old man duly obliged, humbly allowing Constantius to take the purple from his shoulders. It was an extraordinary, unprecedented and still inexplicable moment, but it saved the Constantinian dynasty. Vetranio retired to Prusa in Bithynia, a down-at-heel Hellenistic market town, where he lived on unmolested for another six years.

Constantius was now in command of two field armies to Magnentius’s one, but the events of the past year had proved to him how dangerous the absence of sufficient dynastic oversight could be. The field armies, their officer corps now closely linked to the civilian establishments of the regional prefectures, would prefer to make an officer on-the-spot emperor rather than accept a sole ruler who was far away in another part of the empire. Constantius thus decided to recall Flavius Gallus from confinement in Nicomedia. Gallus was the elder son of Julius Constantius and of Galla, the late sister of the prefect Vulcacius Rufinus who had brokered the peace between Constantius and Vetranio. Gallus had been allowed to survive the massacre of 337 because his sister, now dead, had been Constantius II’s first wife. Now, on 15 March 351, Constantius raised his half-cousin Gallus to the rank of caesar and sent him to Antioch to keep the dynasty visible and dissuade Persian advances by the very fact of his presence.

To solidify the relationship, the 25-year-old Gallus was married to Constantius’s eldest sister Constantina, who was much older than the new caesar and had previously been married to Hannibalianus, one of the victims of 337. The plan was good in theory, but the imperial couple made themselves profoundly disliked in Antioch during the three years they resided there – and that despite the fact that the administration of the east remained firmly in the hands of officials personally loyal to Constantius, especially the praetorian prefect Thalassius.

In the short term, however, the appointment of a new caesar meant that Constantius could deal with Magnentius. He took the normal invasion route from the Balkans across the Julian Alps via Emona and Aquileia, but Magnentius was able to stop the invaders there and deny them a free run of the North Italian plain. As Constantius’s army retired to regroup, Magnentius pursued it into Pannonia. Although some of Magnentius’s commanders went over to Constantius – among them the general Silvanus, who would later be made magister militum per Gallias and fall victim to the emperor’s paranoid fear of conspiracy – the two armies took the field at Mursa (now Osijek in Croatia), just beyond Cibalae on the highway to Sirmium. The battle was remembered as the worst in fourth-century history, with unspeakable losses on both sides. None the less, it was the eastern troops who emerged victorious: though nearly half their number lay dead on the field, two-thirds of Magnentius’s field army had been wiped out and the usurper himself was forced to retreat to Italy. The mauling suffered by the victorious army encouraged trouble on the Danubian border and Constantius had to launch a punitive campaign against the Sarmatians to remind them of imperial potency.

After that, in 352, the emperor crossed the Julian Alps, this time without opposition, and took control of the North Italian plain. The rest of the peninsula was in his hands by early autumn. He overwintered in Italy, then crossed the Alps into Gaul at the start of the campaigning season in 353. In a battle at Mons Seleucus (today in the French Alps) Magnentius was defeated again, and committed suicide shortly thereafter on 10 August. His brother Decentius hanged himself at Senonia (Sens). As luck would have it, this was the year of Constantius’s tricennalia, thirty years since he had been raised to the rank of caesar. Like his father before him, he did not trouble to go to Rome to celebrate it. Instead, the ceremonies took place at Arelate, the sometime residence of Constantine. It was a city now entering the height of its good fortune, in an era when the southern Gallic aristocracy was enjoying an unprecedented flowering of talent and artistic ascendancy in Latin literature. The Gallic poet Ausonius, later famous as both a writer and a statesman, was just now beginning a career that would one day celebrate Arelate as Gallula Roma, ‘the little Rome of Gaul’.

Southern Gaul would go on to play a pivotal role in the history of the western empire, and another recurrent feature of late imperial politics first becomes visible with the defeat of Magnentius: though just another failed usurper, he was recast as a barbarian invader. The sources make much of his having been the son of a Frankish father and a British mother, implying that he was not actually a Roman but a foreign foe. Of course, no one had noticed any of that while Magnentius was alive, and his background was not a problem for the impeccably aristocratic Gallo-Romans who supported his regime. Even today, there are authors who make Magnentius’s parentage evidence for the barbarisation of the Roman elite, but they are missing the point: the ruling class of the fourth century was so diverse that regional and ethnic origins were noticed, but were not in themselves markers of either barbarism or ‘Roman-ness’. And in the same way that an emperor’s memory had long been subject to public erasure – damnatio memoriae – a usurper could be retrospectively ‘barbarised’ after his political failure, reimagined as a permanent outsider to the Roman state.

Our insight into the process is possible in part because, with Constantius’s victory over Magnentius, we are suddenly much better informed about the empire’s political history than we have been for the earlier fourth century, thanks to the survival of the Res Gestae of Ammianus Marcellinus, one of the last great classicising works of Latin history, and the last to survive in any bulk. Ammianus was a Greek from one of the prominent Syrian cities, probably Antioch. He came from a good family that had been excused from its obligation to serve in the local town council and was instead closely linked to the larger imperial administration. He was, in other words, a typical product of his era: well connected, ambitious and owing his social distinction to the family’s participation in the state apparatus. As a young man, Ammianus served as protector domesticus, one of that elite group of soldiers who carried out a variety of special functions and often operated in the close vicinity of the emperor himself.

The institution can be seen as a sort of officer training academy, socialising young men from diverse backgrounds, with little common linguistic or cultural ground, into a shared military ethos: in the protectores, an educated urbanite like Ammianus learned to work not just with others like himself, but with men only a generation removed from labour in the fields and with favoured nobles from Francia, Alamannia or Iberia. They all learned to communicate in a standard military Latin, and were taught a basic, stereotyped version of Roman and Greek history so that those who lacked a proper education could still navigate elite society as officers. Thus prepared for life in the camps, palaces and towns, protectores usually moved on to command units of active service troops in later life. For the same reason, close proximity to the imperial person and the military high command meant that more than one former protector went on to become emperor himself.

Ammianus, for those reasons, was personally involved in a number of high-profile missions, and ultimately joined the invasion of Persia launched in 363 by Julian, Constantius’s successor. But his promising career came to a sudden halt when Julian was killed and he chose to pursue the research that would inform his history of the Roman empire – a gift to posterity on which we will never cease to rely. We know that he travelled widely, and that he moved from his native Greek east to Rome. He wrote much of his history there, perhaps under the patronage of one of the great senatorial families. It was probably finished within a year or so of 390 and Ammianus may have died soon afterwards. His Res Gestae intermixes a political history of the empire with all sorts of learned digressions and, most unusually for an ancient historian, with Ammianus’s personal reminiscences. It ran, originally, from the reign of the emperor Nerva (r. 96–8) to that of Valens (r. 364–78), but much of it was lost in antiquity and the surviving text begins with the events of summer 353. The whole of the Res Gestae is shaped by the catastrophe that befell the emperor Valens at Adrianople in 378, when much of the eastern field army was destroyed in a single afternoon. The whole narrative is filtered through that battle’s retrospective significance and a sense of penetrating gloom, but, thanks to its survival, we can study the years between 353 and 378 in greater detail than we can any other phase of Roman imperial history after Tacitus’s Historiae break off in AD 68.

When the extant text of Ammianus picks up, it is 353 and we are plunged into the aftermath of Magnentius’s defeat and suicide. Constantius has put a fearsome magistrate named Paulus Catena – Paul ‘the Chain’ – in charge of hunting down and extirpating the usurper’s followers (we know few details, only that the magister militum Gratianus, father of the future emperors Valentinian and Valens, went into retirement at this moment and was lucky to survive it). Paul was a notarius, on the staff of the primicerius notariorum: technically, then, he was a shorthand-writer and part of the palace secretariat but, like the agentes in rebus, who served under the magister officiorum as a secret police, notarii were often selected to undertake disparate and distasteful tasks. That was because notarii and agentes (who were technically in charge of the imperial post) tended to come to the attention of the emperor’s most intimate officials for their discretion, their loyalty and their willingness to do unpleasant things, which meant that they were regularly seconded to sensitive or specialist duties. With their ill-defined jobs and wide-ranging practical power, notarii were naturally disliked by most other sections of the government.

Paul, in Ammianus’s account, struck fear into all those he investigated because of his relentlessness and brutality. He was, for Ammianus, typical of the creatures Constantius favoured, and the historian paints a chilling picture of the emperor: morose and paranoid, terrified of plots swirling in the background, convinced that anyone he trusted would betray him. The vigour with which Paul the Chain was encouraged to root out those who had sympathised with, or just acquiesced in, Magnentius’s usurpation shows, for Ammianus, the perversity with which Constantius ruled the empire.

What Ammianus never says outright, but clearly believed, is that Constantius wasted enormous energy on Christianity: the number of church councils Constantius sponsored are contemptuously denounced as a drain on time and resources, clogging up the imperial postal service and public roads as bishops were shipped from council to council at public expense. There is something in this, actually. We have already seen the efforts that the emperor made to impose a homoian creed on those parts of the empire under his direct control, and the extent to which that had poisoned relations with his brother Constans. Thus in 351, immediately after Mursa, Constantius not only regrouped to continue fighting, but also immediately summoned a council at Sirmium to work out a creed that would be acceptable to both eastern and western bishops. It failed to do so, but the mere attempt tells us a lot about Constantius’s priorities. Again in 353, while Paul the Chain was hunting down rebels, Constantius was calling a church council at Arelate to compel recalcitrant western Nicenes to subscribe to the creed of Sirmium. Some, like Hilarius, bishop of Pictavium (Poitiers), refused and were sent into exile; others conformed with ill grace. The credal controversies of the reign were far from over.

In the east, meanwhile, Constantius’s paranoia was being fed by the behaviour of the caesar Gallus, whose appointment the emperor had swiftly come to regret. Constantius could not bear the thought of his caesar exercising actual power – he and the emperor’s sister Constantina were meant to represent the dynasty, not act for it. But Gallus got a taste of actual responsibility in 352, when an abortive rising in favour of Magnentius by someone named Orphitus needed to be put down. He also suppressed a Jewish revolt in the same year. Then, in 353, Gallus collided with the eastern administrators Constantius had appointed, and the officials got the better of him. Ammianus makes much of Gallus’s oppressiveness and irascibility, and it is clear that Gallus did in fact order the execution of a bouletes, or town councillor, of Alexandria, and that the order was carried out by Clematius, the comes Orientis, the eastern official equivalent to vicarii elsewhere in the empire. Clematius was reprimanded by the eastern praetorian prefect Thalassius, who reported directly to Constantius. Gallus already resented Thalassius, but now they fell out completely. The caesar tried to stir up the Antiochene mob against the civilian administration, insinuating that the provincial governor Theophilus was hoarding grain. Food shortages were an unfortunate but constant feature of Roman urban life, and never failed to bring mobs into the streets. Theophilus was duly lynched and Thalassius demanded that the emperor bring Gallus to heel.

When the prefect died suddenly, of natural causes, Gallus thought he had won, but he underestimated his imperial cousin’s anger. Constantius sent Gallus a new prefect, Domitianus, carrying letters of reprimand that summoned the caesar back to court to answer for his conduct. Units of the scholae palatinae accompanied Domitianus, to serve as the caesar’s escort. Gallus defied the order and there was a stand-off for much of 354, while Constantius campaigned across the Rhine from a base at Rauracum (now Augst, near Basel). Then, when Domitianus again tried to enforce the imperial orders, Gallus had his personal guardsmen kill the prefect. The senior magister militum in the east, Ursicinus, was then ordered to seize Gallus and deliver him to the western court. Constantina went ahead of them, hoping to calm her brother’s fury, but she died of natural causes somewhere en route. Gallus dragged his heels on the long westward journey, lingering at Constantinople to watch the chariot races, doing so from Constantius’s seats in the imperial box. With that presumption, he signed his own death warrant.

In autumn 354, having traversed the great military highway of the Balkans through Naissus, Siscia and Sirmium to Histria, he was arrested by his own guard captain, Barbatio, and stripped of the imperial robes that marked him as caesar. From there he was shipped to Pola, tried by a tribunal headed by Constantius’s cubicularius Eusebius and executed along with three friends who were accused of having corrupted him. The complexity of the corporate government that is revealed in the Gallus episode reminds us that it was Constantius who completed the transformation of the imperial bureaucracy into a fully-formed state apparatus, building upon the innovations of his father and the tetrarchs. Equally noteworthy is the role of the cubicularius Eusebius in Gallus’s trial. Cubicularii were heads of the emperor’s household staff, but their proximity to the imperial person meant they would be entrusted with many other sensitive tasks. It was Eusebius who had concealed Constantine’s will to Constantius’s advantage, and he served his emperor throughout the latter’s lifetime. Cubicularii were frequently eunuchs, as Eusebius was, and, because the emasculation of Roman citizens was banned, eunuchs were almost always foreigners, mainly from Persia or the Caucasus. That lent them a sinister air that would linger over the office of cubicularius even when it was not held by a eunuch, and it is part of the reason that Eusebius was as hated a member of Constantius’s inner circle as Paul the Chain.

With Gallus dead, his associates had to be investigated, and Paul was again given the commission. Constantius himself spent the winter of 355 in Mediolanum and he is not attested outside of northern Italy again until the following year. While in Mediolanum, and no doubt anxious about developments on the Persian front, he found something else to worry about in Gaul. There, in 355, the magister militum per Gallias, a man named Silvanus, is said to have seized the purple. In fact, this so-called usurpation was no such thing, but rather a tragic deception, cooked up by rival factions in the palatine administration. Silvanus, like Ammianus Marcellinus among many others, had prospered as a young man because of his family’s imperial service: his father, Bonitus, had served Constantine in the wars against Licinius and, again like Ammianus, Silvanus had begun his career young, we may presume in the corps of the protectores domestici. As his career flourished, he built up a network of support among the palatine and military administrations. From Ammianus, we have a very good general sense of how these fourth-century political networks worked, as a series of regional factions, with alliances threaded across the empire and its near frontiers, men from different groups favouring others from their own region and reaching out to build alliances in other regional networks. Even as we concentrate on the person and actions of the emperor, it is the background rumble of such factional rivalries that explains much of late imperial history. The case of Silvanus, which is so well known only because Ammianus took part in it personally, can stand as an example of how palatine factionalism claimed its victims.

What appears to have happened is this: Silvanus was still a relatively junior officer when Magnentius’s coup presented him with an opportunity for promotion. In that, he was similar to a great many other Gallic and Frankish men in the western establishment who found themselves neglected by the Balkan regime of Constans. A tribune of a guard unit, Silvanus had cannily switched sides just before the bloodbath at Mursa, and as a reward he was promoted after the Constantian victory to the rank of magister peditum per Gallias. That made him the senior military commander in Gaul, taking charge of the western military establishment from his residence at Colonia Agrippina. Constantius was no fool. In choosing Silvanus, he reckoned on the fact that the Gallic establishment would respond better to one of its own than to someone who had marched west with Constantius. But that meant promoting Silvanus over the heads of Constantius’s own more trusted supporters, and military men are sensitive to slights over rank and precedence.

Constantius’s magister equitum Arbitio immediately began plotting against Silvanus, knowing just how easy it was to prey upon Constantius’s paranoia. He suborned a junior officer name Dynamius to request a letter of reference from Silvanus; having done so, Dynamius erased the letter’s contents, but kept the signature, and then redrafted it to suggest that Silvanus was plotting rebellion. Constantius’s praetorian prefect at the time was C. Ceionius Rufius Volusianus signo Lampadius, a privileged member of the Italian aristocracy and an ally of Arbitio’s (the signum, or nickname by which a man chose to be called, is a characteristic affectation of fourth-century aristocrats). Lampadius received the forged letter in confidence and presented it privately to the emperor, who became enraged and summoned his consistorium. There, in the presence of his senior officials, he denounced Silvanus and the conspirators named in Dynamius’s forged letter, but two of the guard tribunes, Malarichus and Mallobaudes, both of them Franci, protested loudly that something was amiss, causing the emperor to stay his hand for a time. During that pause, Dynamius produced a second forged letter in which he tried to implicate Malarichus, and to insinuate that a Frankish court faction was plotting against the emperor. Malarichus learned what was going on, brought the forgery to the emperor’s attention, and a commission of enquiry was empanelled to get to the bottom of the affair. It rapidly discovered that the letters were forgeries and Dynamius was duly punished. But what happened in Gaul was worse.

Because Ammianus was complicit in Gallic events, he had every reason to keep the ugly truth under wraps and so he peddles the official version at face value, contradictory and implausible as it is. According to our author, Apodemius, the same agens in rebus who had brought the news of Gallus’s execution back to Constantius, was sent to Gaul to summon Silvanus to answer charges, but instead spread the word that the magister militum had already been condemned to death. Hearing that grim news – and believing it, given the emperor’s personality – Silvanus proclaimed himself emperor. Now in open revolt, he awaited the arrival of the emperor’s representative, his high-ranking peer Ursicinus, on whose staff Ammianus was serving. Ursicinus’s orders were to suppress Silvanus, and that is what he did. The two generals commiserated, to be sure, both lamenting the fate of good men like themselves under an emperor such as Constantius. But that did not stop Ursicinus from doing his job: on Easter Sunday, when the pious Silvanus was leaving church and suspected nothing, Ursicinus’s guard of protectores, Ammianus among them, set upon him and cut him down as a usurper.

Except he was not and the story is a lie. Silvanus may never have lifted a sword in anger against Constantius, and it is certain that he never seized the purple. There are no coins. The first thing a usurper always did was to strike coins in his own name: the most ephemeral emperors of the third century are known to us solely through their coinage, and even short-lived fourth-century pretenders like Domitius Alexander (311) or Nepotianus (350) have left a relative profusion of coins for the modern numismatist to ponder. For Silvanus, there is nothing, and it will not do to protest that being based at Colonia Agrippina he had no access to a mint in the few weeks of a short reign – the region had seen a profusion of irregular Notmünzen (as the Germans succinctly call unofficial emergency coinage) during the dying days of the Magnentian regime, the mint at Trier was close by, and makeshift mints had been available to every other usurper in late Roman history. Silvanus cannot have been uniquely handicapped in this respect, which means he never proclaimed himself Augustus. On the contrary, he was murdered by a crack force of imperial guardsmen, led by one of the emperor’s most successful generals, and he was murdered because once the rumours about him had reached a certain pitch, it no longer mattered whether they were true: an emperor like Constantius would condemn a man for such charges, even if he knew them to be false, pour décourager les autres. Even so, that sort of emperor would not feel safe. Distance, jealousy, ambition were incubators for usurpation, and though both Gallus and Silvanus had been false alarms, at some point a real threat would arise. So, despite the precedent of Gallus, Constantius turned once again to a relative.