`Now that the whole empire had devolved on Constantine, his arrogance increased and he was carried away with his success.' - Zosimus, late fifth century.2
n i May 305 the tetrarchs simultaneously held two grand parades on opposite sides of the empire. Diocletian and Galerius were just outside Nicomedia, and Maximian and Constantius were at Milan. The cities were the most common residence for the two senior emperors, but in Diocletian's case the spot had a particular significance, for it was there, just over twenty years before, that the army had proclaimed him emperor. Now, aged about sixty and in poor health, he formally resigned his office. Maximian simultaneously did the same at Milan, although subsequent events would make it clear that he acted unwillingly. Galerius stood beside Diocletian and Constantius beside Maximian, and the two Caesars were now each promoted to the status of Augustus. To aid them in their task two new Caesars were appointed. Diocletian unclasped his purple imperial cloak and draped it over the shoulders of Galerius' nephew Maximinus Daia. By the same gesture, Maximian elevated the general Severus to the imperial college.
No senior officer or official can have been surprised by this carefully orchestrated power change, for preparations must have been underway for some time. The promotion of Constantius and Galerius was anticipated, but some sources claim that the choice of Caesars surprised at least the junior ranks in the army. Constantius and Maximian both had adult sons who seemed more obvious candidates. Severus was a close associate of Galerius and it is clear that the latter expected to dominate the new tetrarchy just as Diocletian had controlled his imperial colleagues.'
It is impossible to know when and why Diocletian decided to resign. Some scholars see it as a long-held plan, fundamental to his concept of the tetrarchy, but this is surely too schematic. It is more natural to see his regime as developing gradually and not part of some master plan. He had recently recovered from a serious illness and he may simply have lacked the strength or the enthusiasm for the task of ruling the empire. The Christian writer Lactantius, who until a few years before had taught rhetoric in Nicomedia itself, claimed that Galerius pressured the ailing emperor into resigning and then selected the new Caesars himself. We need to be cautious, because Lactantius disliked both men, because they had persecuted the church and his book described the gruesome fates of all who did this. Yet it is undeniable that the new regime was built around Galerius, and in recent years he was the best placed of the tetrarchs to influence Diocletian. Even so, the latter had always proved single-minded in the past and it may be that he believed Galerius was the best choice.4
However willingly, Diocletian resigned. For the moment, as in the past, Maximian was unable to resist his more forceful colleague. The empire had four new rulers, one of whom expected to impose his will on the other three and impose solidarity. He failed. It is doubtful that Galerius was as good a politician as Diocletian, but the main difference was the existence of potential rivals with a good enough blood claim to imperial power to rally support. As in the past, one usurpation tended to encourage others. The first came in Britain, just over a year later.
Constantine
Constantius' son Constantine was in his early thirties when he witnessed the acclamation of Galerius and Maximinus Daia at Nicomedia. He had already proved himself a capable officer, fighting on the Danube and against the Persians. For a while he remained with Galerius and stories subsequently circulated of attempts by the latter to engineer his death - ordering him to lead a charge and then withholding reserves, and even commanding him to fight a lion single-handed. Finally, when his father requested that he come to join him in Britain, Constantine is supposed to have slipped away quietly. Using the imperial post with its system of relay stations and fresh mounts, he rode hell for leather to escape, killing the horses he did not need to prevent pursuit. Reaching the bedside of his dying father at York, Constantius had just enough breath left to name him as his successor. Most of this tale is probably romantic invention. In fact, we know that Constantine spent several months in Britain with his father. This was important, for it permitted him to build up a rapport with his senior officers and officials.'
Constantius died in York on 25 July 306 and Constantine was immediately proclaimed as his successor by the senior army officers there, backed by their troops. For the moment he claimed only the rank of Caesar and sent envoys with an image of himself in imperial regalia to Galerius, seeking his acknowledgement. This was duly given, in marked contrast to Diocletian's rejection of the claims of Carausius. Galerius also now promoted Severus to the rank of Augustus, completing the tetrarchy once again. However, the appearance of stability did not last.
Maximian had retired to a villa in Italy and his son Maxentius was in Rome in October. Earlier in the year Galerius had issued a decree extending Diocletian's system of taxation to cover Italy as well as the provinces, ending more than four centuries of the region's exemption from direct taxation. Maxentius fed off the unpopularity of this and was proclaimed emperor at Rome by a range of supporters including the praetorian guard - the last time it would make an emperor. Maximian came out of retirement to back his son, once again calling himself Augustus. This time Galerius and Severus were adamant in refusing to accept any more additions to the imperial college.
Severus gathered an army at Milan and marched on Rome in 307, but almost all of his officers and soldiers had been commanded by Maximian before his retirement. They showed no enthusiasm for fighting against their old commander and soon began to desert. Severus fled, but was captured, held prisoner and forced to resign as Augustus. In the autumn Galerius invaded Italy, but he was unable to force the enemy to risk an open battle and was not prepared for such a major undertaking as besieging Rome so late in the year. It is claimed that he was amazed at the sheer size of a city that he had never seen before - a striking reaction from the ruler of the Roman world, but a sign of the city's now marginal importance. Galerius withdrew and did not repeat the attempt. Maxentius responded by having Severus killed, making full reconciliation unlikely.'
During this period Constantine campaigned on the Rhine frontier, winning the victories that were expected of an emperor. He did not formally break with Galerius, but nevertheless dealt with Maximian, marrying his daughter Fausta at Trier in 307. (Maximian's older daughter Theodora seems to have died some years before her husband Constantius. She was not the mother of Constantine, for he was the product of an earlier liaison - there is considerable doubt that it was a legal marriage, and Constantine's mother may have been Constantius' mistress rather than his wife.) Maximian proclaimed Constantine as Augustus. He had already squabbled with his own son so remained at the court of Constantine. The Roman world now had five emperors.7
In 308 Diocletian came out of retirement to support Galerius. They met with Maximian at Carnuntum on the Danube and appointed as Augustus an officer named Licinius, who was another close associate of Galerius. Maximinus Daia and Constantine were confirmed as Caesars, but permitted to call themselves `sons of the Augusti'. Maxentius was ignored, but was anyway kept busy by the rebellion of a usurper named Domitius Alexander, who had been proclaimed in Africa and was not suppressed until the following year. After the conference Diocletian went back to cultivate cabbages at his palace in Sirmium - he is supposed to have boasted about their flavour - and Maximian also resumed his retirement.8
Diocletian's intervention brought an uneasy truce, but also showed just how far the stability of the tetrarchy depended on the imperial college being dominated by one man. In 310 Maximian once again decided to take back power and rebelled against Constantine. He was swiftly suppressed and executed. Both Constantine and Maximinus Daia soon took back the title Augustus - the latter was said to have been very bitter after seeing first Severus and then Licinius promoted over his head. Galerius died the next year - he was suffering from cancer of the penis and his last days were said by Lactantius to have been particularly unpleasant. Licinius and Maximinus Daia rushed to carve up his territory, eventually accepting a
division at the Bosphorus. Diocletian may have died around the same time, but there are a number of traditions about his end, some claiming disease and others suicide.'
In 312 Constantine attacked Maxentius. His army was loyal, toughened by campaigns on the frontiers, and he was a very capable general. Marching quickly, he defeated Maxentius' subordinates in northern Italy and then approached Rome itself. The city's walls offered it protection from sudden assaults, but such a long circuit wall was difficult to defend against a properly organised attacker. It would also have damaged Maxentius' prestige to skulk behind defences against a challenger whom he seems to have substantially outnumbered. He led his army out and crossed the Tiber at the Milvian bridge - the stone bridge had been demolished, so a pontoon bridge had been constructed next to it. In spite of their numbers, neither general nor army was a match for their opponents, and Constantine won an overwhelming victory. Maxentius was killed and many of his panicking soldiers drowned when they streamed across the pontoon bridge and it collapsed under their weight.'°
Three emperors were left and Constantine and Licinius now allied. In 313 Licinius married Constantine's half-sister Constantia (one of the children of Theodora), before he led his army eastwards against Maximinus Daia. The latter had crossed into Europe and advanced along the main road through the Balkans. They met near the city of Adrianople on 3o April and Daia's army was routed. He escaped, but was hunted down and committed suicide in July. The two emperors left standing now agreed to split the provinces between them, Constantine taking the western and Licinius the eastern provinces.
In 316 Constantine provocatively crossed into Licinius' territory during the course of a campaign against some Sarmatian tribes. If he hoped to provoke a war and not simply assert his seniority, he may have been shocked to find his enemy stronger than expected. There were two battles, the second once again near Adrianople, but although Constantine won both, his victory was not overwhelming. In a negotiated settlement Licinius gave up almost all of his provinces in Europe. In 324 the struggle was renewed. Once again, the road system shaped the campaign and Constantine won his first victory near Adrianople. Licinius retired to Byzantium, but lost a naval battle and then fled to Asia Minor. Constantine pursued and won a final victory at Chrysopolis. Licinius surrendered and was allowed to go into comfortable captivity. Some time later he was charged with conspiracy and executed, along with his infant son. Constantia was spared and lived on as an honoured member of the imperial court."
For the first time in almost forty years the empire was united under a single emperor. It is true that during his reign Constantine named several of his sons as Caesars, but there was never any doubt that he was supreme. Going further than Septimus Severus, who had merely `found a father', Constantine had long since spuriously declared himself the descendant of the brief, but honoured Claudius II. He made no attempt to revive the tetrarchy and his success rather undermines modern claims that it was now essential to have more than one emperor. Like Diocletian he was a `strongman' who defeated all his opponents and intimidated any other potential challengers. Unlike Diocletian he chose not to do this through taking and dominating imperial colleagues, but preferred to rule alone. The success of both men had far more to do with personality, political skill and single-minded ruthlessness, than with any of the institutions they employed. Altogether Constantine was an emperor for thirty-two years, although he only controlled the entire empire for thirteen."
The Church
Constantine is famous as the emperor who made the empire Christian. The truth is a good deal more complicated than this, and the preceding narrative has deliberately omitted any mention of his religion. This is not because it was not significant, but because he needs to be understood first as one of the many - though admittedly one of the most successful - usurpers who competed for imperial power in the third and fourth centuries. This was the context of his conversion, and of his religious attitudes and policy. It is misleading to transfer the novelty of his faith to analysis of his political career. Perhaps more than at any other time, there is a great danger of turning a history of Constantine's reign into essentially a history of Christianity - and especially orthodox Catholic Christianity - during these years, simply because this was the concern of the overwhelming majority of the sources.
For a generation after Gallienus called off his father's persecution of the Church, Christian communities across the empire had been free from systematic persecution. This promoted the already pronounced trend for Christianity to become much more visible. Bishops, as Paul of Samosata's controversial career at Antioch had shown, often became wellrecognised local dignitaries. Churches were built openly in many towns and cities - there was one next to Diocletian's palace in Nicomedia. There were Christians in many walks of life, including the army and imperial administration, and only occasionally did some of them find that their beliefs became incompatible with their official duties. Tacitly, Christianity seemed to be accepted and no longer seen as a threat to the empire. The wild rumours of cannibalism and incest had largely gone, and many people had a much clearer idea of what the Christians believed. The Neoplatonist philosopher Porphyry based his attacks on the Church on a very detailed knowledge of Jewish and Christian scriptures."
There had been a last burst of persecution under the tetrarchy. Diocletian is supposed to have first become concerned when the priests conducting an unsuccessful augury blamed the failure on Christians in the crowd making the sign of the cross. In 297 all imperial officials and soldiers were required to display their loyalty by performing a sacrifice. Some Christians resigned in response, more probably did just enough to conform, and a few openly refused and were executed. In 303 there was a more concerted move against the Church, prompted in part by a fire in the palace in Nicomedia, which was blamed on Christian arsonists. The focus of the new round of persecution gives a good idea of just how well established and public the Christian movement had become. Churches were targeted - the one next to the palace in Nicomedia was the first to be demolished - and associated assets were confiscated. All Christian scriptures were to be handed over to the authorities and burned. Rather than seeking out every Christian, it was mainly the leaders who were arrested and torture was employed to force them to recant. Those who refused were imprisoned, subjected to more savage coercion and in due course often executed if they continued to resist.
As in the past, Diocletian's main aim was to impose outward conformity and unity throughout the empire. Again, as in earlier persecutions of the Church, much depended on the enthusiasm of governors and other local officials. In some regions it was strongly pressed and extremely brutal, and probably all the more shocking to a Christian community that had been free of such attacks for decades. Diocletian was an enthusiastic persecutor, Maximian and Galerius somewhat less committed, and Constantius decidedly lukewarm. The latter demolished churches, but does not seem to have executed anyone.14
The Christians were not the only group to suffer in these years. In 302 Diocletian had also ordered the persecution of the followers of the prophet Mani. Born in Persia in 216, the latter had travelled widely, including a visit to India, and the religion he created showed the influence of Jewish, Christian, Zoroastrian, Buddhist and other ideas. Diocletian seems to have viewed the Manichees as potentially subversive because of their presumed sympathy with the Persians. In his decree he claimed that they `had sprung forth very recently like novel and unexpected monstrosities from the race of Persians - a nation hostile to us - and have made their way into our empire, where they are committing many outrages, disturbing the tranquillity of the people and even inflicting grave harm on the civic communities'. He feared that in time they would `infect the modest and tranquil Roman race ... and our whole empire'. It is doubtful that his suspicion was correct, for although Ardashir and Shapur I had treated Mani with respect, their successors had persecuted the cult, executing the prophet himself in 276.Is
Persecuting the church was scarcely Diocletian's greatest
priority in the last years of his reign, although it obviously dominated the accounts of our Christian sources. After his resignation, Galerius and especially Maximinus Daia were enthusiastic persecutors, but again, often had other more important concerns. There is very little evidence that by this time the wider pagan population had much enthusiasm for persecuting Christians. In his last days Galerius issued a decree admitting that persecution had failed to stamp out Christianity. Therefore, Christians would now be permitted freedom of worship and allowed to rebuild their churches, although their confiscated property was not restored. As a result, `it will be their duty to pray to their god for our safety and for that of the state and themselves, so that from every side the state may be kept unharmed and they may be able to live free of care in their own homes'. Within less than a year Maximinus resumed the persecution, refusing to enforce Galerius' decision. Replying to one petitioner he blamed the Christians' abandonment of the old cults for all the ills of the world, such as war, plagues and earthquakes.'
Both Constantine and Maxentius adopted a benevolent attitude towards the Christians when they first seized power, not wanting to alienate any potential supporters. The latter's enthusiasm seems to have cooled once he became more secure. Constantine's father Constantius had not only been very restrained in the years of persecution, but seems to have had a number of Christians in his household. For himself, he remained devoted to the worship of Sol Invictus (the Unconquered Sun) - the popular supreme god whose protection Aurelian had claimed. Throughout the third century there was a tendency amongst many pagans towards a form of monotheism, revering one deity above all others, and perhaps seeing the various gods and goddesses as merely manifestations of a single divine being. Several of the main philosophical schools had taught similar ideas for centuries. Whatever the specific nature of Constantius' beliefs, he certainly did not feel any great hostility towards Christians and may have had a good deal of sympathy, although the `closet' Christianity claimed for him in later years is unconvincing. Constantine appears to have begun with a similar attitude. Like many people in the ancient world, he believed profoundly in the power of the gods to communicate in dreams. In 310 one panegyrist proudly asserted that he had been granted a vision by the sun god Apollo and this was reflected on his coinage .17
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