18

CONSTANTIUS, JULIAN AND THE EMPIRE TO COME

While Paul the Chain investigated the intimates of Silvanus and some Alamanni seized the opportunity to attack Colonia Agrippina, Constantius remained in Italy. There, at Mediolanum on 6 November 355, he elevated his sole remaining male relative – his cousin Julian, half-brother of the late Gallus, to the rank of caesar.

We last met Julian at Nicomedia, in 337, after the summer of blood. There, he would later remember, he enjoyed an idyllic boyhood in the care of the eunuch Mardonius, before an unwelcome transfer to the supervision of bishop George of Cappadocia, who kept him under the equivalent of house arrest on the large imperial estate of Macellum. It was not until 348 that Julian was set free and left to his own devices. These took him to Constantinople, where he studied with the pagans Nicocles and Themistius, the latter a very important figure in the reigns of four emperors, and the Christian Hecebolius; then to Pergamon, to learn from the philosopher Aedesius, an heir to the neo-Pythagorean sage Iamblichus; and finally to Athens, where the theurgist Maximus became his spiritual guide. It would later emerge that, over time, Julian had abandoned the Christian faith of his hated uncle Constantine and instead embraced a vivid and highly baroque form of traditional pagan ritualism. This he blended with an esoteric and heterogeneous stew of third-century mysticism and theosophism. In 355, he kept this profound conversion experience, and the anti-Christian fervour that accompanied it, deeply buried. Rather than the pagan zealot he would prove, Julian seemed like a somewhat wayward intellectual, unkempt and argumentative in the usual manner, but also the last surviving member of the dynasty on whom Constantius might perhaps rely – though the senior emperor did so with some reluctance, and even then only at the urging of his wife Eusebia.

In the end, Constantius summoned Julian from his studies at Athens and made him caesar at Mediolanum. After a month together, Constantius escorted Julian from the city and entrusted him with the care of Gaul. Like Gallus, Julian was expected to be a figurehead, and his officials would not be of his own choosing but of Constantius’s alone. Unlike Gallus, he would be given some opportunity to act his part and learn to command an army, of which he had no experience, but only under the watchful eye of men the augustus trusted more than him. While Eusebia gave him a copy of Caesar’s Gallic War to educate him about the lands to which he was heading, Constantius went so far as to write out in his own hand a memo documenting the subordinate position he expected his cousin to maintain. He permitted only one of Julian’s intimate friends, and only four of his old servants, to accompany him – everyone else was a creature of Constantius. In time, as Julian became ever more successful, these restraints would poison relations between the two emperors, but in 355 the Roman world appeared to be at peace.

That being the case, Constantius turned once again to the enforcement of his doctrinal views. The refusal of many western bishops to sign up to the creed of Sirmium had been a source of maddening frustration to the emperor for a couple of years, but now, in 355, he had agentes in rebus out bullying bishops into adherence. The bishop of Rome, Liberius – not yet a ‘pope’ or head of the western church in the way his successors would become – was summoned to a personal audience with the emperor at Mediolanum, where he was browbeaten for his resistance to the acts of Sirmium. Liberius was a powerful figure in the city of Rome and also the first Roman bishop to articulate fully the idea that his place as the putative successor of the apostle Peter gave him particular claims to moral authority. Constantius had him exiled in 355.

More or less simultaneously, Athanasius of Alexandria was deposed and exiled for the umpteenth time, Constantius correctly perceiving him to be the figurehead of empire-wide resistance to the homoian creed of Sirmium. Constantius was willing to harass but not to execute church leaders, and he seems genuinely not to have understood why so few of those he wished to have cooperate with him were willing to do so. Compounding Constantius’s frustration was the public and evident care he took to be a good Christian emperor – in some ways a better one than his father, though he could never replicate the latter’s status as the deliverer of Christians from persecution. And yet Constantius tried. Early in 356 he promulgated an edict making sacrifice to the images of pagan gods a capital offence and, though he allowed pagan temples to remain standing and temple priests to maintain their properties, they could no longer carry out any cult acts to their gods. Constantius also explicitly demanded that all Romans abstain from sacrifice. His clear intention was to put an end to traditional cultic practice altogether.

In 357, he made a triumphal visit to Rome to celebrate his victories in Persia and Julian’s in Gaul, entering the city on 28 April. Waspish contemporaries carped that his only real successes had come in wars against his fellow Romans, but if the eastern wars had been inconclusive, Julian’s victories in Gaul were real enough. The narrative in which Ammianus Marcellinus recounts Constantius’s entry into Rome is one of the great set pieces of late Classical literature, and Ammianus, despite his intense dislike of the emperor, could not help but admire the control and self-possession with which Constantius conducted himself, every inch the figure of the aloof and distant lord of the world. While in Rome, the emperor had both the altar and the statue of Victoria removed from the senate house at Rome, a gesture for his fellow Christians and a sign that he would not have the business of the Roman state conducted in a place where sacrifice might still be offered. That this action met with very little protest is a signal of the surprising speed with which the imperial government, and imperial magistrates, were becoming Christian.

Although he did not yet know it, Constantius’s edict was a direct blow to his cousin Julian, whose pagan philosophical beliefs had continued to develop in Gaul. His fortunes had prospered as well, as he laid the groundwork for a massive campaign into Alamannia. In summer 356, Julian accompanied an army led by Constantius’s generals Marcellus and Ursicinus and invaded Alamannia via Germania Prima, re-enforcing Colonia Agrippina en route. The army then retired to winter quarters, dispersed throughout northern Gaul, rather than base itself at a major imperial residence like Trier – it may be that the damage done by the civil war against Magnentius was such that a campaign army could not have been kept supplied in a single location. Julian wintered with his guard troops at Senonia, deep in the north Gallic interior, and nowhere near its military or administrative nerve centres. This may have been Julian’s choosing to wilfully defy his cousin’s generals, or else they may have been trying to keep him away from places where he might recruit sympathisers among soldiers and bureaucrats. One way or another, it was courting disaster, for the whole of northern Gaul remained insecure – the civil war had denuded its garrisons and Silvanus had not been given much of a chance to restore order on the frontiers. As a result, Julian found himself besieged in Senonia by a large Frankish war band, and had to hold out for several months behind the city walls. Julian blamed Ursicinus and Marcellus and convinced Constantius to replace them with a much less powerful figure, the magister equitum Severus.

But rather than allowing him to deal with the Franci, Constantius ordered Julian to carry out the invasion of Alamannia that had been planned since Julian became caesar. Severus, with Julian in tow, advanced across the Rhine into Alamannic territory, while Constantius’s senior magister peditum, Barbatio, crossed the upper Danube in Raetia Secunda. The two armies, however, failed to make their planned rendezvous, Julian having stopped to win some minor engagements in the Rhineland rather than listening to Severus and executing the plan as intended. Barbatio withdrew from Alamannia as a result and, though Ammianus suggests he did so deliberately to endanger Julian, it showed good strategic sense once the Roman pincer movement had failed. Seeing that, the Alamannic king Chnodomarius turned on Julian and met him at Argentoratum (modern Strasbourg), where Julian found himself vastly outnumbered – supposedly 13,000 to 35,000, though the latter number is undoubtedly inflated. That the Roman triumph was total is a reminder of how rarely barbarian armies could win an open battle against a well-disciplined Roman force: Julian disposed his men on a narrow front, harassing the Alamannic infantry with his cavalry before launching an infantry advance that broke the Alamannic line and led to their total rout.

We say that Julian did this because the sources, not least his own account, tell us so. It is perhaps more likely that old Severus had done much of the actual planning, but after the victory Constantius began to allow Julian more latitude, even supporting the caesar against his own praetorian prefect in a dispute over whether to levy an extraordinary tax to cover a shortfall in 357. Seemingly to his own surprise, Constantius was finding Julian a useful partner. Though as augustus he properly took credit for the Gallic victories in his Roman triumph, he no longer felt obliged to police Julian as closely as he had once done. The latter overwintered in Lutetia (modern Paris), again demonstrating his preference for the interior provinces of the Lugdunenses over the traditional administrative centres in the Rhineland. By now he was almost certainly beginning to plot against his cousin, and the victory at Argentoratum had given him a new hold on his troops’ personal loyalty. An easy victory in Francia, more a show of arms and a training exercise than a campaign, followed in 358, further cementing those bonds.

As yet, however, Constantius had no inkling of his cousin’s evolving plans – or indeed of his secret paganism and continued interest in theurgy – and he had other problems to worry about. The Persian front was again unsettled as Shapur prepared for another assault on Roman territory, while Constantius’s relationship with fractious western bishops had worsened still further. Latin churchmen had decisively rejected continued Greek hair-splitting over the terminology of ousia (or substantia in Latin), insisting that nothing could improve upon Nicaea. But Constantius remained insistent that all churchmen subscribe to an identical creed, even though he had finally learned that bringing eastern and western bishops together in a single council was not just pointless but actively counterproductive. He therefore determined to hold two councils, one at Ariminum (Rimini) in northern Italy and the other at Seleucia-on-the-Calycadnus (modern Silifke in southern Turkey), then the most important city in Isauria. The creed Constantius offered at Ariminum was presented by a trusted bishop from the Balkans, Valens of Mursa, and left out controversial words like substantia. Despite that, the Balkan bishops were much distrusted by their Italian and Gallic counterparts: they were too close to the emperor, doing his bidding rather than demonstrating proper episcopal independence. The westerners duly rejected the creed of Ariminum, reaffirmed the sufficiency of Nicaea alone, and excommunicated Valens and two of his supporters. Constantius himself was far away, off beyond the Danube fighting the Sarmatians, and the western bishops who travelled to Sirmium to inform him of the council’s decision were forced to wait there for several months.

During this time, the other western bishops were detained at Ariminum by imperial troops, forbidden to return to their sees, which made a mockery of Constantius’s supposed efforts at compromise. In the short term, however, the heavy-handedness seemed to pay off. Without reference to their fellow bishops back at Ariminum, those waiting at Sirmium for Constantius to return revoked the excommunications and accepted the creed of Ariminum, if only to allow themselves to go home. Constantius thus never met with the bishops who had come from the western council, instead taking the highway back to Constantinople as soon as his campaigns were finished. There he was met by not one but two delegations from the council at Seleucia in Isauria, which had failed as comprehensively as Ariminum had done. One faction, led by Basil, the powerful bishop of Ancyra in central Anatolia, insisted on a creed that not only discussed the fraught term ousia but did so in a way that could easily be described as neo-Arian. The imperial creed, sponsored in Latin by Valens of Mursa, had been pushed at Seleucia by Acacius of Caesarea, and both sides were so intransigent that they demanded adjudication by Constantius himself. Late in December 359, Constantius met in person with the competing delegations and extracted from Basil’s party adherence to the creed of Ariminum. Early in 360, he summoned another council, to Constantinople, to proclaim the creed of Ariminum as the uniform creed of the empire. For the first time there was little demur and fewer than the usual number of exiles, but the sham consensus would not outlive the emperor, and the ripples of this theological controversy will occupy us time and again in the sequel to this volume.

While Constantius had been in Sarmatia, Julian had continued to fight on the Gallic frontier. Winter 358–9 was again spent in Lutetia, and at the start of the next campaigning season he crossed the Rhine at Moguntiacum (Mainz), inflicting a major defeat on several Alamannic kings and publicising their surrender widely. This self-promotion was more than Constantius, as suspicious as ever, could bear. He recalled Julian’s most trusted officials, particularly his quaestor sacri palatii Salutius Secundus, and instead sent him a new set of court advisers – the hated Paul the Chain and two others, Pentadius and Gaudentius, the former of whom had been active in the downfall of Gallus in 354. This provocation led Julian from cautious ambition to open revolt. Constantius’s young caesar timed his coup well. Had he acted any sooner, Constantius would have been free to leave the eastern provinces unattended and crush his errant relation. By 359, Persia was once again a problem.

Despite periodic blustering on both sides in the earlier 350s, the decisive war threatened by both Roman and Persian rulers had never materialised, largely because of disruptions on the distant Central Asian edge of Shapur II’s empire. These were the result of huge changes to the dynamic of the empire still further east, in the Hexi corridor of north-western China, which we will consider at some length in the sequel to this volume. Broadly speaking, they represented far-ranging military actions on the part of various steppe nomads all claiming descent from the Xiongnu (or Huns). In the 350s, neither the Persians nor the Romans had any idea of what was going on in eastern Eurasia, but Shapur was kept occupied on his eastern frontier for much of the 350s. By 358, however, the most immediate challenges had been suppressed, and at least one Hunnic clan had allied itself to Shapur as his clients. The shahanshah immediately began to muster a campaign army to make good on earlier plans to attack the Roman frontier and retake long-disputed territories. Negotiations occupied much of 359, but Shapur refused to give up his demand that Constantius surrender the eastern Roman provinces to him. It is now, for the first time, that we have good evidence for a Sasanian ruler actually claiming to be the successor of the Achaemenids Darius and Xerxes and using the extent of Darius’s empire as a justification for his demands.

Constantius reappointed Ursicinus to high command as magister equitum, placing him in charge of the preparations to meet the invasion. We know a great deal about this campaign because Ammianus Marcellinus took part in it and expounds in detail the hardships faced in the Persian siege of Amida. It is clear that the Roman field army had not been properly deployed when the invasion began, because Ursicinus himself was almost taken in an ambush by the Persian cavalry while inspecting some frontier defences. As so often, however, the great cities of Mesopotamia proved capable of stopping a Persian army in its tracks, when the garrison at Amida killed the son of Shapur’s royal client Grumbates – a king of the ‘Chionitae’, according to Ammianus, though we cannot be sure which Hunnic clan he commanded – against whom Shapur had until recently been campaigning. To satisfy Grumbates, Shapur consented to a full-scale siege of the city, in the winter of 359–60, and the ability of the Amidan garrison to hold off the besiegers for a couple of months forced Shapur to withdraw and prepare another attack for the following year.

Julian would have known of the problems on the Persian front almost as soon as they began – a close friend of his, a philosopher named Eustathius with whom he had once studied at Pergamon, was part of the embassy that failed to avert the Persian invasion. Then, in February or March 360, while still in winter quarters at Lutetia, Julian received an order from Constantius demanding a levy of western troops to assist with the Persian campaign, and not a light one either: four entire infantry units and 300 men from every other unit in the Gallic army. It was a reasonable request, given the scale of the threat Constantius faced, but Julian used it as an excuse for his own imperial proclamation. This he had clearly planned in advance: for the first time since he went to Gaul, he had assigned units of the field army winter quarters at Lutetia, and not merely his own guardsmen. Julian would always claim, as was traditional, that he accepted the rank of augustus with deep reluctance and in response to his soldiers’ spontaneous demand. But the fact that the whole Gallic army supported his move suggests that it had been prepared well before units had settled into their winter quarters, and that selected officers had been at work over the winter plotting the coup. Two elite units, the Celtae and the Petulantes, were the first to acclaim Julian Augustus at Lutetia, but the rest of the Gallic army fell into line at once.

Julian must have realised that Constantius’s reaction would be hostile, but he did not immediately press the issue, instead bloodying his troops in punitive razzias through Francia. Constantius was cautious, too. He received an embassy from his cousin, which suggested that Julian should be augustus in the west but remain a mere caesar in the east – a proposal the emperor rejected, demanding that Julian renounce the title of augustus and content himself with caesar. By Constantian standards, it was a moderate reaction, but there was little more he could do because of the Persian situation.

Deprived as he had been of western levies, Constantius could not launch a counteroffensive against Shapur, whose armies took Singara and Bezabde on the extreme edge of Roman territory in summer 360 and razed the former city. In winter 360–61, Roman armies retook Bezabde, but there was no avoiding a full-scale war with the shahanshah. The question was when it would come, given that now civil war loomed, too. In November 360, Julian celebrated his quinquennalia at Vienna (modern Vienne in France), the capital of the important province of Viennensis. He did so in the full garb of an augustus and also minted coins with that title, knowing full well that Constantius would find that intolerable. The latter wintered at Edessa, vacillating between a Persian and a civil conflict.

In early 361 Julian mobilised his army, ostensibly for another raid into Alamannia. There he captured a king named Vadomarius, known to be a personal client of Constantius, who – Julian now claimed – had ordered Vadomarius to attack Julian. This casus belli was undoubtedly spurious, but it was all Julian needed. He marched along the Danube into the Balkans in high summer, transhipping part of his force downriver in advance, and taking all the major cities as far as Sirmium by the end of summer. Nevitta, his magister equitum and most trusted general, took the main land route through Raetia and Noricum, down the Sava, into the central Balkans.

The plan was to occupy the western part of Illyricum and meet any advance by Constantius there, while sending a few units into Italy across the Julian Alps to seize the North Italian plain. Strategically it was an excellent plan, save that two of these units rebelled en route to Italy, suborned by agents of Constantius, and took up position in the stronghold of Aquileia. Julian might now face a war on two fronts, or have his supply lines to the loyal Gallic provinces cut off. He therefore halted at Sirmium to await events, while some of the units he had left behind in Gaul marched into northern Italy and occupied the garrison cities there. Julian occupied himself with composing letters to the public of the eastern cities, justifying his actions and accusing Constantius of all sorts of villainy. That left Constantius no choice but to leave the eastern front to its fate and deal with his rebel cousin. In October 361, he set out westwards at the head of his army, but he made it only as far as Cilicia when sickness overtook him. He died on 3 November and, in an act of great statesmanship, he named Julian his legitimate successor on his deathbed. There would be no rival proclamations, and Julian could inaugurate his sole reign as the last emperor of Constantine’s dynasty.

The death of Constantius marks the end of this book’s narrative, a hinge on which late imperial history turns. Constantius had more than anything else cemented the structural strengths, and political dynamics, of his father’s revolutionary reign. After the tetrarchic experiments had rendered permanent the ad hoc experimentation of the third century, and brought to its culmination the gradual process of equestrianisation on which we have spent so much time, Constantine institutionalised a new, more expansive, more intrusive and more complex state than the Roman world had ever known. The long and surprisingly stable reign of Constantius ensured that there would be no counter-revolution, and that the bureaucratic state of the earlier fourth century would go from strength to strength in the decades to come. In religion, too, Constantius made permanent his father’s legacy. Though Julian – famous to posterity as Julian the Apostate – attempted to unmake the imperial Christianity that his relatives had embraced and increasingly enforced, he could only imagine an anti-Christian empire and not a meaningful return to the religious landscape of the pre-Constantinian era. That he died very soon after his accession to sole rule meant, if anything, the further entrenchment of a Christian political and ecclesiastical establishment as the very heart of imperial legitimacy.

Julian, though a strangely bitter man, was also a starry-eyed idealist. His immediate impulse upon succeeding his cousin was a massive invasion of Persia that went disastrously wrong. The aftermath, which saw the imperial campaign army having to extract itself at great cost from enemy territory, showed how remarkably powerful the military high command, the palatine bureaus and the establishments of praetorian prefects had become: the later fourth century is a great age of collective government, regional and bureaucratic oligarchies tussling with one another while ensuring that those who became emperor – Jovian, Valentinian and Valens, and Theodosius – were junior officers unable to impose their will on events even when they were individually competent and authoritative. Other seeds planted in the reigns of Constantine and Constantius bore fruit in the course of the later fourth century. The ideological, political and economic power of the Christian church, the entrenchment of its priestly hierarchy, and its ever greater patterning on the geographies of the Roman state were all far advanced by the century’s end, as too was a growing body of canon law meant to guide and bind Christian believers.

East and west diverged in this, as in many things, with Greek and Latin Christianity revealing ever more fundamental differences of thought and habit that have never been bridged since. The eastern and western empires became politically and economically more distinct from the 360s onwards as well. The growing dominance of Constantinople to the life of the Greek world is part of the story, but so too is the eastern empire’s control of a source of new gold in the Caucasus to which the western empire had no access. One consequence of that was of tremendous significance: the ruling elite of the east was far more closely bound to the structures of the imperial state, which monopolised the currency supply, than was the western elite, where society’s uppermost strata could get along, if pressed, without much help from the structures of government. That, more than anything, explains the generation-long collapse of western imperial government in the middle of the fifth century, while the eastern government was left essentially unscathed. It also helps explain why the western empire was less able than the eastern to cope with changes to the much wider Eurasian landscape – a brief but consequential few decades in which various Xiongnu or Hun empires remade political boundaries from China to India to central Europe.

Two hundred and fifty years ago, Edward Gibbon began his story of Rome’s decline and fall more or less where we began ours, in what he saw as a golden age of the Antonine emperors. So captivated was he by his tale of the ‘barbarism and religion’ that brought down the empire that he carried his narrative forward to the conquest of Constantinople by the Ottoman Mehmet II, over a millennium later. All of us who write on the later Roman empire, or more broadly on the cultural world of what we now call Late Antiquity, tread in Gibbon’s footsteps and in the shadow of his intellect, his prose and his ambition. But no one today would attempt to match his scope. This volume and the one that follows cover a very specific set of stages in the journey from the early Roman empire to a Greek Roman empire in the east standing alongside a post-imperial west. We have moved from an empire ruled by Romans to an empire filled with Romans, and from a Rome whose horizons were those of a somewhat expanded Classical Mediterranean world to a Rome that was one of Eurasia’s four great civilisations in an era of archaic globalisation.

The Roman empire of later Late Antiquity, which we will look at in our next volume, was unrecognisably different from the Roman empire of Hadrian, but it was recognisably heir to the empire Constantine had remade on the foundations laid first by Severus and then Diocletian – who could, strange though it is realise, at least imagine himself restoring a pristine Roman past that Hadrian would have recognised. We need not decide here the extent to which that vision corresponded to reality, any more than we need decide, in the next volume, how much the successors of Constantius and Julian knew that the empire they were slowly remaking was a product of Constantine and his revolutionary reign. Their ideas and their actions are story enough.