The Tetrarchy from Diocletian to Constantine: Emperors of Rome

Emperor Diocletian decided to retire in April 305, assuming that the system for sharing imperial authority that he had set up would continue along the same lines. However, things did not run as smoothly as he had hoped.

Diocletian had split the empire into twelve “dioceses”, with each of four “tetrarchs” running three of them apiece. He and Maximian were the two senior tetrarchs, with Constantius and Galerius being subservient to them. Diocletian’s plan was for Maximian and himself to retire at the same time, with Constantius and Galerius moving up to fill the senior positions (“Augusti”) and two new men being appointed to be junior emperors (“Caesares”).

The original thought had been that the sons of Constantius and Maximian, namely Constantine and Maxentius respectively, would be the new Caesars, but Diocletian changed his mind on this. He subsequently announced that the new junior emperors-in-waiting would be a general named Flavius Valerius Severus and Maximinus Daia, who was a nephew of Galerius.

The problem was that not all the new men who took office on 1^st May 305 were content with what Diocletian had decreed. In particular, Constantius was annoyed that his son Constantine had been excluded from the succession.

It was not long before this source of dissent turned from being a potential problem to an actual one. Constantius was responsible for Britain and it was while he was in Britain in July 306 that he died at Eboracum (York). The army, presumably following the expressed wish of Constantius, declared Constantine to be the new emperor.

Meanwhile Maxentius, who was the other man to lose out when Diocletian changed his mind about the succession, refused to let matters lie and claimed the position that Diocletian had assigned to Severus. His father Maximian gave him his support, which was essential in deciding the issue because the army, which had served under Maximian, refused to back Severus who was imprisoned and eventually killed.

In 307 Galerius invaded Italy, hoping to defeat Maxentius and restore the arrangement that Diocletian had decreed. Constantine refused to take sides and Rome, protected by the walls erected 30 years previously by Aurelian and Probus, proved to be capable of withstanding a siege. Galerius had no choice but to withdraw.

On the other hand, Galerius did have a powerful friend to call upon for help, namely Diocletian who was quietly growing cabbages on his estate at Split (in modern Croatia). A conference was called in 308 at Carnuntum (in modern Austria), under the chairmanship of Diocletian, at which it was agreed that Constantine could continue to rule the regions he already controlled and Galerius would continue as the other senior emperor. A new junior emperor was appointed to replace Severus, this being a general named Licinius.

With civil war avoided, Diocletian went back to his vegetables and Galerius was happy to be recognized as the most powerful person in the empire. Unfortunately for him, he only lived to enjoy this status for another three years, dying of natural causes (a very nasty case of bowel cancer) in May 311.

The surviving emperors, who now all regarded themselves as Augusti rather than Caesares, then divided into two factions, Maximinus allying himself with Maxentius and Constantine with Licinius. One result of Diocletian’s reforms had been that the army, as well as the government, had split into what were virtually independent camps that were loyal to one or other of the tetrarchs. The result was that each of the four men controlled roughly equal forces, so any power struggle was likely to result in a highly destructive civil war.

In the event, the struggle boiled down to a contest between Constantine and Maxentius. Constantine was a strange character who exhibited a range of personality traits, one of which was a deep belief in divine intervention. The question was, which god to trust? He had long been a devotee of Sol Invictus – also known as Elagabal, the Syrian sun god who had originally been introduced to Rome by Elagabalus and then re-introduced by Aurelian. Constantine now decided to place his trust in the Christian god.

The story of Constantine’s conversion has become a legend, not least because of the profound implication it would have for the growth of Christianity as well as the later history of the Roman Empire. The truth of what happened is less easy to ascertain. However, the fact remains that Constantine was able to defeat Maxentius, and he ascribed his victory to what he termed the “Divine Mind”.

After the final battle with Maxentius at the Milvian Bridge on 28^th October 313, at which Maxentius was killed, Constantine was clearly the most dominant figure in Roman politics, and the Tetrarchy, such as it now was, was no longer a government by equal parties. 

© John Welford

Constantine I, Emperor of Rome

Constantine was one of the most influential of all the emperors of Rome. His reign marked a definite turning point in the history of the empire, which would never be the same again. He must also be counted as the last truly “great” emperor of Rome. Although there were other notable emperors after his time, nobody was of anything like the same quality.

That is not to say that Constantine was a perfect emperor – far from it. He was an enigmatic character who is very difficult to assess. He may have been the first emperor who became a Christian, but he did not always behave in what most people would regard as a “Christian” way. Indeed, he was capable of great cruelty at the same time as displaying tolerance and acting wisely. His actions can also be seen as making the eventual fall of the western empire inevitable.

His rise to power

Constantine was born in (probably) 275 in Naissus, which is modern Nis in Serbia. His father was Constantius, who would become one of the four co-emperors known as the Tetrarchs who divided the empire between them at the behest, and under the control, of Emperor Diocletian. Constantius took on this role in 305, having control over Gaul and Britannia.

When Constantius went to Britannia in 306 to sort out a local uprising he took Constantine with him, which meant that when he died at Eboracum (York) in July 306 the army was only too ready to proclaim Constantine as his successor, although the job should have gone to the man who had been nominated for this role by Diocletian (Flavius Valerius Severus).

Constantine’s reign lasted for nearly 31 years, but it took 18 years for him to become sole emperor. Those years were a period both of sharing power and of eliminating his rivals.

They were also years of shifting loyalties, with the various would-be emperors working out where their best moves lay. The two main players at this stage were Maximian, who had been co-emperor with Diocletian and who been forced to retire from power at the same time that Diocletian did, and his son Maxentius.

Maxentius was able to get Constantine’s support for his own claim to be a co-emperor by giving Constantine his sister Fausta in marriage, despite her very young age – it would be nearly ten years before they started living together as husband and wife.

However, Maximian, who had always resented his forced retirement, tried to persuade Constantine to attack Maxentius, which Constantine was not prepared to do. Instead, Maximian tried to usurp his son by ripping the imperial robe off his shoulders. When Maxentius’s guard intervened, Maximian had no choice but to back off, after which he sought sanctuary with Constantine at Treveri (modern Trier on the border between Germany and Luxemburg).

This arrangement continued until 310 when Maximian tried to seize power when Constantine was away on campaign. The attempt failed and Maximian committed suicide.

Maxentius continued to be co-emperor in Rome, with control over Italy, Spain and Africa, despite the fact that his position was unofficial and another co-emperor, Licinius, was supposed to be doing that job.

In 312 Constantine took a big risk by deciding to challenge Maxentius head-on. It was at this point that Constantine appears to have had some sort of experience that convinced him to change his religious attitude. He was clearly a deeply pious person, but his devotion had up to now been towards Sol Invictus, the “Unconquered Sun”. This deity had its origins in Syria, and the cult of Sol Invictus had first come to Rome courtesy of Emperor Elagabalus, who had been the chief priest of the cult before unexpectedly becoming emperor. Worship of Sol Invictus lapsed after the fall of Elagabalus but had been re-introduced by Aurelian, who had made the cult one of the official Roman religions.

What exactly happened to Constantine, and when, is far from clear, mainly because later Christian writers were keen to see Constantine’s “conversion” as a major event in the history of Christianity and to treat it as something similar to St Paul’s vision on the road to Damascus. There are various stories, including that Constantine was visited by Jesus Christ in a dream and told to paint the “chi rho” symbol on his soldiers’ shields before going into battle. Another is that Constantine looked into the sky and saw the sign of the cross and the words “with this be victorious”.

A more likely explanation is that Constantine, seeking support from Sol Invictus, saw a phenomenon known as a “solar halo”, caused by sunlight being refracted by ice crystals in the upper atmosphere.

At all events, Constantine did not abandon his previous beliefs on the spot and suddenly become a Christian. It may well be that he saw Jesus Christ as Sol Invictus in another guise. When new coinage was issued later in his reign it was Sol Invictus who was portrayed alongside the emperor, and when a “day of rest” was instituted for the empire, it was “Sol Day” – Sunday – that was chosen.

What we do know is that Constantine began his campaign against Maxentius having placed his trust in the “Divine Mind”, although it is far from clear what he meant by this. We also know that he conducted the campaign with considerable skill and that he swept all before him after he entered Italy. It was not long before he reached Rome and waited for Maxentius to face him in battle.

The battle in question, fought at the Milvian Bridge across the River Tiber, was decisive. Whether or not Constantine’s men fought with Christian symbols on their shields, they were utterly victorious and Maxentius was among those who were killed. Constantine could now enter Rome in triumph.

Constantine did not stay long in Rome and was soon on his way back north. He was well aware that his next challenge was likely to come from the fourth co-emperor, namely Maximinus, who had allied himself with Maxentius. Constantine met his own ally, Licinius, to whom he gave his half-sister Constantia in marriage. Licinius was clearly expected to deal with Maximinus.

That is what happened. Maximinus had crossed the Dardanelles with an army and met Licinius near Adrianople (west of modern Istanbul), where he was soundly beaten. Licinius chased his retreating force back into Turkey and caught up with them at Tarsus, where Maximinus committed suicide. The four tetrarchs were now down to two.

The Roman Empire now effectively split into two halves – east and west – with each comprising six of the 12 dioceses established by Diocletian. The two emperors governed their realms with very little reference to each other and neither – at first – showed much interest in challenging the other for complete control.

However, problems arose when it came to planning for the succession if and when either of them should die. In 315 and 316 both of them became fathers of sons. Constantine already had a son, namely Crispus by his first wife Minervina, but Constantine was not sure whether he wanted Crispus to be his chosen heir. When Licinius’s son was born, the two men came to an agreement that neither son should succeed, but that the heir for both halves of the empire should be Bassanius, the husband of Constantine’s half-sister.

But then along came Constantine’s son by his second wife Fausta, and he changed his mind. If anyone wanted evidence that Constantine’s apparent conversion to Christianity did not include a change of heart in favour of Christian morality, his machinations in favour of his family’s interests should prove the point. Bassanius was promptly executed on a trumped-up charge and Constantine prepared to make war on Licinius.

However, things did not go all his own way. Licinius proved to be a tough nut to crack and Constantine could only conquer one of the three Balkan dioceses held by Licinius. He was forced to accept a compromise over the succession that recognized the claims of both infant sons as well as that of Crispus. The treaty that settled this was signed in March 317 and stayed in force for the next seven years.

By 324, Constantine and Fausta had produced two more sons and a daughter. Seeing himself as heading a potentially powerful dynasty, Constantine saw no reason why his family should share the imperial throne with anyone else and decided to get rid of Licinius for good.

This was achieved without too much difficulty. The civil war began in the summer of 324 and was all over by November. Licinius was sent into exile but then suffered the same fate as the unfortunate Bassanius. There was no doubt now as to who ran the Empire.

 

The first Christian emperor

With the Christians of the Empire now free from persecution, they proceeded to do what religious fundamentalists have delighted in doing down the ages, namely persecute each other. The relatively young religion was riven with disputes over matters of theology, and Constantine was well aware that this was a potent source of unrest. He decided to step in and knock some heads together.

The dispute that caused most upset, and which was to have the most profound implications, arose when a priest in Alexandria, named Arius, had a sharp disagreement with his bishop, named Alexander. This was over the nature of Christ and his relationship with God the Father. Arius maintained that the two were “of different substance” and that the Son was subservient to the Father. Alexander held that they were “of the same substance” and the Son (i.e. Jesus) had existed for all time as opposed to being created when “born of the Virgin Mary”.

Arius and Alexander each had many supporters for their point of view, and the issue – in Constantine’s view – could only be settled by bringing all the parties together and reaching a decision that would have the imperial seal of approval. The grand council met at Nicaea, in what is now Turkey.

The result was a statement of belief known as the Nicene Creed, ostensibly composed by Constantine although probably drafted by advisers, which (in amended form) has been the basic statement of belief held by most Christian denominations ever since. It was a compromise between the two opposing camps, although it supported Bishop Alexander’s view much more strongly than that of Arius.

Given a free choice, many modern Christians might think that Arius’s theory had much to recommend it – it does seem to make more sense logically – but they are not given that choice. For this they have a semi-pagan Roman emperor to thank whose grasp of theology was shaky at best and who may well have decided that the view of a bishop held more sway than that of a mere priest. Whatever the case, the decision stuck.

Constantinople

The other major reason why Constantine was the most influential emperor of the later Roman Empire was his founding of a new capital city for the eastern empire, which for many centuries bore the name Constantinople.

Constantine was well aware that the future of the empire depended on securing the eastern frontiers, in both Europe and Asia, and Rome was too far from either to be where the emperor should be based. The ancient city of Byzantium was an ideal location for an eastern base, being within striking distance of several likely trouble spots, and this was therefore Constantine’s choice.

Byzantium occupied a triangular peninsula on the north side of the Bosphorus strait that connects the Black Sea to the Sea of Marmara. Constantine’s new city could therefore be protected by the sea on two sides and by a new wall on the landward side. It was not long before the new city outgrew the original wall and new defences were built in the 5^th century by Emperor Theodosius II.

Another advantage of Byzantium was that seven hills could be distinguished within its area, which meant that it could be seen as a symbolic mirror of Rome, which was traditionally built on seven hills.

Constantine spared no expense in building his new capital, which began with a splendid imperial palace and a hippodrome that could accommodate 80,000 spectators. The city included churches, but older pagan temples were retained. Public buildings such as baths and a senate house were erected, although the senators of Rome were not expected to move to the new city.

The speed of construction was impressive. Begun in 324, the new city was consecrated in 330. This was partly due to elements of some of its buildings, such as columns and tiles, being appropriated from buildings elsewhere in the empire.

Running the Empire, and the succession

With Constantine concentrating his efforts on his new eastern capital, how was the western half of the empire to be managed? At first, his son Crispus was able to do the job, but disaster struck in the year 326. Various accounts exist of what actually happened, one of them involving a love affair between Crispus and his stepmother Fausta, but, whatever the facts, the net result was that Crispus was executed for treason and Fausta died soon afterwards. She may have taken the side of her stepson in an argument with Constantine and suffered the consequences.

Constantine was now left without an empress, so his elderly mother Helena became his ambassador and undertook a grand tour of the east, where Christian tradition asserts that she found portions of the “true cross” in Jerusalem as well as building churches at sacred sites. She was later honoured by the church as St Helena.

The empire, thanks largely to the reforms introduced by Diocletian, was now organized on regional lines in a number of respects, including the army. A strong leader like Constantine could keep all the pieces working together, but what about the future? That was something that gave Constantine much worry in his later years, as he realized that none of the potential candidates for succession fitted the bill.

He had three surviving sons as well as two nephews whom he saw as potential rulers of parts of the empire, but he did not consider appointing a single “Caesar” who would step up to “Augustus” on his death. His plan was evidently to divide the empire into five prefectures, with his nephew Hannibalianus having control of Iraq once it was brought under Roman control. It was while he was planning to invade Iraq in 337 that Constantine fell ill and died.

Constantine’s final act was to have himself baptized as a Christian, having spent his whole life as a dedicated follower of Sol Invictus but with the sneaking suspicion that Jesus Christ and Sol Invictus were two sides of the same coin. He also declared his intention to be buried as a Roman emperor in the mausoleum that he had had built for that purpose in Constantinople. His son Constantius later had the mausoleum consecrated as the Church of the Twelve Apostles, which would probably have annoyed Constantine greatly had he known.

By tolerating Christianity, and even taking an active role in its development, but keeping at arm’s length from it on a personal basis, Constantine made clear that being a Roman emperor and a Christian was perfectly possible without going the whole hog as a “Christian emperor”. This was a lesson that not all of his successors appreciated.

© John Welford

Byzantium, Constantinople, Istanbul

28th March 1930 was the day on which Istanbul officially changed its name from Constantinople, although the new name had been in use locally for centuries before then.

The city, on the Bosporus Strait that separates Europe and Asia, began as Byzantium, a Greek colony founded in the 7th century BC. When the Roman Empire overwhelmed Greece, Byzantium became a free city, albeit under the overall dominion of Rome.

When Emperor Constantine defeated his rival Licinius at the Battle of Chrysopolis in 324 AD, he spent the next night in nearby Byzantium, which was no more than a small town on a peninsula overlooking the Bosporus and the Sea of Marmara. He said afterwards that he had a vision (not the first he had had in his life) in which the spirit of the town, an old woman, became transformed into a beautiful young woman on whose head Constantine placed a diadem. This persuaded him to rebuild and expand the town into a magnificent city.

A few days later he led a party of troops to mark the boundary of his new city, which would be three times the size of the old one and defended by huge walls. In 330 AD he renamed it Constantinople and declared that it would be the new capital of the Roman Empire.

The foundation of Constantinople marked the split between the eastern and western halves of the Empire, with the eastern half surviving for nearly a thousand years after the western half had disappeared. It is always referred to as the Byzantine Empire, although the name of Byzantium had long since been displaced by that of Constantinople.

The name Istanbul derives from “Istinpolin” from the Greek for “in the city”. It sounds as though it might have been the answer to a question like “Where does X live?” or “Where are you going?” At any rate, it was understood by the Turks of Anatolia to be the name of the city, and this is what they called it from as early as the 13th century.

Officially, it was always Constantinople until the change in 1930, but by that time very little remained that was of Greek or Roman origin, and there was certainly nothing left of Byzantium.

© John Welford

The Battle of the Milvian Bridge, 312 AD

The Battle of the Milvian Bridge was fought on 27^th October 312 AD. Although the result of the battle was significant in itself, it was what the victor thought he had seen prior to that battle that was to have to profound consequences for the future of Europe.

The Roman Empire was in turmoil, for neither the first nor the last time, as a plethora of claimants fought for the title of Emperor. The situation eventually boiled down to two brothers-in-law fighting for domination, namely Constantine and Maxentius. After winning a series of battles, Constantine had made his way nearly to Rome with some 50,000 men as against the 70,000 with which Maxentius was defending the city.

On the day preceding the battle, Constantine believed that he saw a flaming cross in the sky, close to the Sun, inscribed with the words “By this sign you shall conquer”.  Constantine was a devotee of Sol Invictus, the sun god, and he took this as evidence that the god of the Christians was endorsed by Sol Invictus. He therefore decreed that his troops should paint the “chi rho” sign on their shields (this being shorthand for “Christ”) and stated that, should he win, he would convert to Christianity.

During the battle on 27^th October, Maxentius tried to lure Constantine’s forces on to a bridge of boats that was designed to collapse under their weight. However, the plan failed and it was Maxentius, together with many of his troops, who ended up drowned in the River Tiber.

Constantine kept to his promise and declared that Christianity would henceforth be tolerated in the Roman Empire and all persecutions would cease. However, he still retained a measure of devotion to Sol Invictus, apparently believing that the Christian God and Sol Invictus were closely linked. This is the reason why the Christian day of rest was declared as Sunday.

Constantine was to exercise a huge influence on the Church, the different factions of which appeared to celebrate their freedom from persecution by persecuting those of their number who expressed differing views. Constantine used his power as Emperor to knock heads together, such as at the Council of Nicaea in 325 that established theological principles that are still observed today.

On the other hand, Constantine was hardly an ideal Christian in terms of his own behaviour, which appears to have included the executions of both his son and his wife, and decrees that included capital punishment by the swallowing of molten lead.

It has been suggested that what Constantine saw in the sky was an unusual but completely natural meteorological phenomenon known as a “solar halo”. Whatever the cause, the effect was certainly dramatic and very long-lasting.

The picture is of the River Tiber viewed from the modern Milvian Bridge.

© John Welford