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

The sons of Constantine, Emperors of Rome

Emperor Constantine had four sons, three of whom he saw as the foundation of a dynasty that would continue his project of reforming the Roman Empire into something that could survive for future centuries. The problem was that his sons did not inherit from him the qualities that might have made that possible.

Constantine’s first son, Crispus, was born to his first wife, Minervina, in around the year 300. However, he died in 326 having been tried, condemned and executed, on his father’s orders, for crimes that have never been fully explained.

The other three sons were born to Fausta, Constantine’s second wife, and were Constantine (born in 316 and known as Constantine II), Constantius (born in 317 and known as Constantius II) and Constans (probably born in 323). The rather confusing names are a clear enough indication of Constantine’s dynastic plans.

Emperor Constantine I died in 337, which meant that his sons were aged 21, 20 and (probably) 14. Constans was certainly a minor at the time, so his elder brother Constantine II  (see above coin) acted as his regent.

Constantius (the middle brother) was clearly the most ambitious and ruthless of the three, and he took it upon himself to eliminate any possible opposition from outside the brotherhood. He therefore ordered the arrest and execution of every other male descendent of Constantius I (grandfather of the three brothers) and his second wife Theodora. There were only two exceptions, namely Gallus and Julian who were his wife’s nephews (Constantius had married a first cousin). The boys (aged under 10) were taken away to be held in virtual house arrest in Diocletian’s former palace.

Fraternal rivalry

In 340 Constans reckoned that he was old enough to take full control of that part of the western empire (Italy and Illyricum) that Constantine I had decreed should be his. However, Constantine II, who was in charge of Gaul, Spain and Britain, saw things differently.

In 340 Constantius, who ruled the eastern empire, called for help from his elder brother to deal with a threat from the Persian empire under Shapur II. Constantine saw an opportunity to attack his younger brother Constans as he passed through Italy, but the boot was on the other foot. Constantine fell victim to an ambush and Constans was thus able to assume control of the whole of the western empire. East and west now harboured deep suspicions about each other’s intentions.

The rivalry between Constans and Constantius expressed itself in a number of ways, including religion. Although they were both nominally Christian emperors, they had their own ideas about the degree to which pagan elements should be allowed to continue in religious practice. There were also debates between churchmen in the western and eastern halves of the empire about the issues that led to Constantine I’s promulgation of the Nicene Creed in 325. Constantius was keen to summon a new council at which the creed would be “improved”.

With the western churchmen being backed by Constans and the eastern churchmen having the backing of Constantius, it seemed for a while that civil war would break out with religion as its prime cause. However, quite unexpectedly, in 345 Constantius backed down and allowed Constans to have his way. It would seem that the future of Christianity was not something that Constantius thought worth fighting over.

Constans would not enjoy his victory for long. The parts of his realm that had formerly been ruled by his brother Constantine felt neglected and a rival for the throne appeared in the form of Flavius Magnentius, the commander of the army in Gaul. In January 350, during a visit to Gaul by Constans, assassins hired by Magnentius attacked and murdered the youngest of the brothers, leaving just Constantius II as the sole survivor.

Constantius was now faced by two threats, namely Shapur in the east and Magnentius in the west, with the eastern problem being the more pressing one. In the event, dealing with Shapur was not as difficult as he first feared and in the summer of 350 he was able to turn his attention westwards.

A job for Gallus

However, Constantius was well aware that running the empire was no longer a job for one man. He now remembered that he had two surviving cousins, namely Gallus and Julian, still languishing in exile ten years after he had placed them there. He gave Gallus the rank of Caesar together with the task of keeping order in the east while Constantius was elsewhere. Julian was also released and was allowed to get himself an education at Constantinople.

The armies of Constantius and Magnentius met in battle at Mursa (in modern Croatia) in 351. It was a victory for Constantius but both sides suffered huge casualties. After a second battle in 353, at Mons Seleucus in Gaul, Magnentius committed suicide.

Meanwhile, Gallus made the mistake of exercising more power than he had been authorized to do. Constantius was not a man to take that sort of thing lying down and he had his cousin executed for treason. The same fate befell another pretender in the west, named Silvanus. Constantius now called on Gallus’s brother, Julian, to be his Caesar in the west while he returned to take full control in the east.

A job for Julian

Julian was an interesting character, not least because he threatened to undo the move of the empire towards Christianity and return it to paganism. He proved to be a wily operator, which was a good quality to have when his boss was a tyrant like Constantius who had already executed just about everyone in sight who was related to him, leaving Julian as the sole survivor.

Julian reckoned that the way to make himself look good in Constantius’s eyes was to arrange matters so that all failures in the western empire could be ascribed to other people. This was what he did when a band of raiders, the Alamanni, invaded his territory and Julian left his commanders to take the blame for the failure to repel them. Almost by accident, Julian managed to capture the king of the Alamanni, which duly impressed Constantius who then began to entrust Julian with real authority.

Julian also copied Constantius by only dealing with officials at one remove – via correspondence and emissaries – thus instilling a sense of fear in them. This ensured that nobody stepped out of line.

However, Julian was also ambitious and he felt that he was destined to become emperor. Constantius may have suspected that Julian could not be entirely trusted, but he had problems of his own to deal with on his eastern front thanks to Shapur II once again threatening to invade.

In the summer of 359 the Persians invaded and besieged the city of Amida (modern Diyarbakır in eastern Turkey). The city fell eventually, but the Persians then withdrew because of the time they had lost in mounting a summer campaign. Constantius knew that they would return, but in order to defeat them he needed more troops, which could only come from the west and be supplied by Julian.

This gave Julian the opportunity he needed to exploit the widespread discontent felt in the west towards Constantius. In March 360 he allowed himself to be declared Augustus and to propose to Constantius that the empire should be split between them, which was a deal that Constantius had no choice but to accept.

In 361 Julian went even further by leading an army into the Balkans, this being an obvious threat to Constantius’s authority. However, before open warfare could erupt Constantius died of a fever, leaving Julian in sole command of the empire. 

© John Welford

Six Roman emperors between Aurelian and Diocletian

The assassination of Aurelian in September 275 ushered in a period of ten years during which the Roman Empire once more descended into chaos. Six emperors came and went before the next strong ruler, Diocletian, came on to the scene.

Tacitus and Florian

Not for the first time in Rome’s history, a group of plotters acted to bring about the end of an emperor’s reign without having much idea about who they wanted to take his place. On this occasion the Senate made an unwise choice by selecting Marcus Claudius Tacitus (no relation to the historian of that name), a senator who was already aged about 75. Tacitus was immediately faced with the challenge of seeing off incursions of barbarians in Asia Minor. He and his half-brother Florian were successful in this, but that was not enough to save the emperor’s skin. He suffered the same fate as Aurelian, being killed by the same group of palace insiders in June 276, while still on campaign in northern Syria.

Florian took over the reins but had an even shorter stay in the top job. He was murdered after only two months by soldiers loyal to Marcus Aurelius Probus.

Probus

Probus was born in 232 in Pannonia and rose through the ranks of the army to become a general. He was determined to knock heads together and end once and for all the destructive power struggle within the higher echelons of the army and government. His way of doing this was to invite the assassins of Aurelius and Tacitus to a dinner, on the pretext of offering a reconciliation between the disparate groups, then having all the guests murdered.

Once he was firmly in power, Probus began the job of suppressing uprisings and incursions at various places throughout the empire. There were several attempted revolts by would-be emperors, which Probus was able to put down without too many problems, and he was also successful in seeing off Franks, Alemanni, Goths, Vandals and others, from Gaul to Egypt.

Probus’s policy was not always to seek battle against opposing tribes. In some places he allowed barbarian groups to settle within the borders of the empire, notably in Gaul and near the Danube. This helped to make up for depopulation caused by war and plague and also to pacify those people who might otherwise have sought to destroy Roman towns and institutions.

Eventually Probus had time to concentrate on domestic matters. These included the completion of the defensive walls around Rome that had been started by Aurelian. He also built temples and bridges in Egypt, planted vineyards in Gaul and worked on drainage projects on the Nile and the Danube.

Of course, he did not do all this work himself! That was done by his soldiers, who were not required to fight once all the incursions and uprisings were dealt with. However, that did not suit everybody in the army, especially as working hard on building sites and in fields was less to their liking than marching up and down on parade grounds and honing their military skills.

Probus fell victim in October 282 to a revolt led by the Praetorian Prefect Carus, who promptly declared himself to be the new emperor.

Carus

Carus was born in Narbonne, France, although nobody knows when. He promptly appointed his sons Carinus and Numerian to the rank of Caesar (deputy emperor), left Carinus in charge of the western empire, and set out eastwards with Numerian to tackle Rome’s old foe the Sassanids.

After the death of Shapur in 272 the Sassanid empire was nowhere near the threat that it had once been, so attacking it was more of a vanity project than a defensive one. However, before battle could be joined, Carus died suddenly in August 283 when the army was in Mesopotamia. The cause of his death is uncertain, although one source said that he had been struck by a thunderbolt – this could, of course, have been a symbolic way of saying that he had been assassinated.

The death of Carus left Carinus and Numerian as joint emperors. Numerian was quite happy to head for home, but the Romans had not gone far when Numerian contracted a serious eye infection, or so it was reported. This meant that he had to travel in a closed litter, so he remained out of sight as the army travelled westwards towards Rome. After a time, people noticed that a terrible stench was coming from the litter, and when it was opened it was found that Numerian had died and his body was starting to decompose.

Did he die of natural causes, or was there some dirty work afoot and had he already been dead before being placed in the litter? The latter was certainly the opinion of the commander of the Imperial Guard, Caius Aurelius Valerius Diocles. He promptly accused the new Praetorian Prefect of murder and ran him through with his sword. This unfortunate man, who may or may not have been guilty, was Flavius Aper who was also Numerian’s father-in-law.

Diocles was now acclaimed as the new emperor, for which role he took the name Diocletian.

Carinus

Meanwhile, Carinus was still ruling the western empire. History has not been kind to Carinus, mainly because it was written by people who were wholly sympathetic to Diocletian, who was seen as the man who saved the empire from chaos and depravity.

The truth would appear to be that Carinus spent most of his brief reign campaigning successfully against barbarians on the Rhine and the Danube and even venturing to Britain.

However, according to some accounts he found time to engage in every vice known to man, outdoing even the worst excesses of Caligula. He apparently married and then divorced nine wives, committed every sexual vice that could be imagined, killed people for the fun of it, and spent vast sums of money on entertainment and luxury. It does all seem a little unlikely, probably resulting from the over-active and warped imaginations of the historians!

What is definitely true is that Carinus had to fight for his throne against Diocletian, the armies meeting in 285 at the River Margus in what is now Serbia. The battle seemed to be going in Carinus’s favour, but he was struck down by an unknown hand, possibly belonging to one of his own commanders who saw Diocletian as a better bet as emperor. If that was what happened, the commander in question was probably correct in his opinion.

© John Welford

Magnus Maximus, Emperor of Rome

Magnus Maximus was a usurper who conquered part of the western Roman Empire and became recognized as emperor, albeit for a relatively short time.

He was probably born in the year 335 in what is now north-west Spain. He joined the army and served under his uncle, General Flavius Theodosius, whose son would later become Emperor Theodosius I.

Magnus rose to the status of General and served in Britannia, where he was active in putting down local uprisings.

Britannia was part of the western empire ruled by Emperor Gratian from November 375, but his rule was not always accepted with complete loyalty. When the army rebelled in 383 they declared Magnus Maximus (which translates as “Great the Greatest”) to be their emperor. He accepted their nomination and was soon having coins minted that showed winged Victory hovering over the two emperors – the western one being Magnus and the eastern being Theodosius.

There were in fact four men (or, to be more accurate, three men and a boy) who claimed the title of emperor at this juncture. The one who most concerned Magnus was Gratian, who was the “official” western emperor with jurisdiction over Gaul and Britannia. Magnus therefore crossed the English Channel, accompanied by a large number of soldiers whose duties had previously been to protect Roman Britain from troublesome local tribes.

Many of Gratian’s troops promptly deserted him and he fled to Lyons, where he was murdered on 25^th August.

Magnus Maximus was now in effective control of much of the western empire, namely Britannia, Gaul and Spain, and he was able to retain that position for the next five years. What he wanted most was recognition of his status by his fellow emperors, namely Theodosius and Valentinian II (Gratian’s half-brother), who was the nominal ruler of Italy, Africa and the western Balkans, despite being only 12 years old at the time of Gratian’s death.

Theodosius was willing to recognize Magnus as a co-emperor, but Valentinian – or rather, his adviser Bishop Ambrose – was not. Magnus had no choice but to resort to force and he therefore invaded north Italy (Valentinian was based at Milan) in 386. Valentinian fled eastwards, accompanied by his mother and sister, and sought refuge with Theodosius.

Theodosius was therefore given the choice of either supporting his cousin Magnus or the half-brother of the man who had nominated him for the post of eastern emperor. He was also offered Valentinian’s extremely attractive sister as his wife, and this was an offer he could not refuse.

Theodosius therefore marched against Magnus Maximus, who was completely unprepared for this turn of events. Magnus was captured at Aquileia (near modern-day Trieste) and executed on 27^th August 388, a fate that was also suffered by his family and close associates.

One important consequence of the short reign of Magnus Maximus was that the troops he took with him to Gaul did not return to Britannia. There is some evidence that many of them settled in what is now Brittany. The result of this was that Britannia was now deprived of much of its defence force and was therefore subject to incursion by tribes that included Picts from Scotland, Scots from Ireland and Saxons from northern Europe. Local chiefs who had formerly relied on Roman protection could no longer do so. The beginning of the end of Roman Britain can therefore be dated from around this time.

© John Welford

Leonidas, King of Sparta

Leonidas was a hero of ancient Greece whose conduct at the Battle of Thermopylae has become a byword down the centuries for selfless heroism against overwhelming odds.

Born in around 521 BC, Leonidas (the name means “lion-like”) was one of the sons of King Anaxandridas of Sparta. He became king himself in 491 BC, succeeding his half-brother Cleomenes.

The invasion of Greece by the Persians under Xerxes, in 480 BC, led to Leonidas’s determination to make a stand against the enemy. He chose 300 Spartan warriors who themselves had sons, so as not to risk the extinction of their families. On his march he was joined by troops from other cities, so his total force was around 7000 before he reached the pass of Thermopylae in August or September (accounts differ).

Thermopylae (the “hot gates”) was of huge strategic importance because it consisted of a very narrow route between a mountain and a morass, and was the only way of gaining access to southern Greece from the north, which the Persian force of at least 100,000 men was seeking to do.

As told by the historian Herodotus some fifty years after the event, Leonidas’s army was able to hold the Persians at bay for two days, inflicting massive casualties on them. However, a traitor named Ephialtes told the Persians about a mountain path that enabled them to skirt round the Greek army and then attack them from the rear.

On hearing of this move, Leonidas realised the hopelessness of his position. He dismissed all the troops except his own Spartans (men from Thespis and Thebes also volunteered to remain) and made a frontal attack on the Persians who confronted him, with the sole aim of selling Greek lives as dearly as possible. In the desperate battle that ensued, Leonidas was an early faller. His body was rescued by the Greeks, and the place where he fell was later marked by a stone lion.

Despite the defeat, the Greeks were emboldened by the courage and self-sacrifice of Leonidas and his men, and redoubled their efforts to repel the invading Persians, which was achieved after the naval victory at Salamis the following month.

Leonidas’s story has inspired military campaigners down the centuries, as well the 2007 movie “300” directed by Zack Snyder, which was itself based an earlier comic-book mini-series.

Alexander the Great was to find himself in the opposite situation to Leonidas during his own invasion of Persia in 330 BC. Unable to force through the narrow pass of the Persian Gate, Alexander sought, and found, a local guide to show him a mountain path by which he could take his men to a position from which he could attack the defenders from behind. 

© John Welford

Decius, Emperor of Rome

Decius was a short-lived Roman emperor who was notable for instigating a period of persecution of the growing sect known as Christians. He held a strong belief that the empire’s problems would be solved by focusing on what had served it well in past centuries, namely military might and devotion to Rome’s traditional gods.

Gaius Messius Quintus Decius Valerinus was born in around the year 201 in Pannonia, which covered parts of several modern countries including Hungary, Austria and Serbia. He was therefore defending his home territory when Emperor Philip (“The Arab”) gave him the task of seeing off the threat of Goths who were advancing across the Danube, which he did successfully in the year 249.

His troops decided that Decius would be a better emperor than Philip and persuaded him to “don the purple”. There is a suggestion that he was highly reluctant to accept, but that did not prevent him from marching towards Rome and meeting Philip in battle at Verona. Philip was killed and Decius became the undisputed emperor.

A new Trajan?

Decius celebrated his accession by pretending to be greater than he was. He did this by changing his name to Gaius Messius Quintus Traianus Decius in the apparent belief that he was a latter-day Trajan. A deeply superstitious man, Decius took to heart an ancient prophecy that a king

“will rule mighty Rome, skilled in war, emerging from the Dacians, of the number 300”

Decius was pushing the analogy to its limit, given that he was from Pannonia rather than Dacia, but he took the “number 300” to refer to the Greek latter Tau, this being the initial of Traianus, and Trajan had conquered Dacia at the beginning of the previous century, so perhaps Decius thought that he fitted as the fulfilment of the prophecy.

Religion and persecution

Decius took the decline of Rome to be due to general neglect of the ‘ancestral gods’ so his solution, begun in the year 250, was for all subjects of the empire to make formal sacrifices, for which proof was needed. The sacrifices had to be performed in front of officials, and evidence has survived of written declarations of sacrifice with the signatures of witnesses.

Not surprisingly, this demand did not go down well with Christians within the empire, with the result that the short reign of Decius was a period of religious persecution. Noted martyrs from this period, who were later recognized as Christian saints, included St Christopher, St Agatha, and St Fabian, who had been an early Pope.

Despite all Decius’s efforts, the sacrifices did not provide the protection for the empire that he had anticipated. Goths continued to invade from the north across the Danube, added to which a terrible plague swept across the empire.

Fighting the Goths

Decius spent much of his time in 250 and 251 trying to get to grips with the Goths, but this proved to be extremely difficult. Roman armies were used to fighting pitched battles, which they usually won, but these barbarian tribes refused to play by the rules. They preferred what today we would call “guerilla” tactics, namely carrying out sudden raids on unprepared units of troops then retreating back into hiding before they were ready to strike again.

In 250 Decius’s army was ambushed, with severe losses, after which the city of Philippopolis (in modern Bulgaria) was laid waste. It was not until June 251 that Decius was able to catch up with the Goths, who lured the Romans into swampy terrain at Abrittus (in modern Romania) and destroyed them.

This battle, which is also known as the Battle of Forum Terebronii, was one that the Romans should have won. General Trebonianus Gallus failed to press home his advantage, which allowed the Goths to counterattack. Gallus’s legions survived relatively unscathed but the rest did not. Decius and his son Hostilian were both killed, leaving Gallus to pick up the pieces and be declared the next emperor.

© John Welford

Diocletian, Emperor of Rome

Diocletian was one of the more effective later Roman Emperors and also had the distinction of being the only Emperor to abdicate his throne voluntarily.

Gaius Aurelius Valerius Diocletianus was born in Dalmatia, probably in 245, of obscure parentage. He had a career in the army under Emperors Aurelian, Probus and Carus, and was on campaign with Carus in Mesopotamia in 283 when the latter died suddenly. Legend has it that his tent was struck by lightning, but this could be taken as meaning that he was murdered by mutineers.

Carus had two sons, Carinus and Numerian, the latter of whom was on campaign with him while Carinus remained at home. Numerian was murdered in the summer of 284, but his assassins had no idea what to do next and pretended that their victim was still alive but suffering from an eye infection that prevented him from appearing in public. Eventually the stench from the rotting corpse became too powerful to ignore and the senior officers realised that they had to choose a compromise candidate for Emperor to set against Carinus.

The choice fell upon a mid-ranking officer called Gaius Aurelius Valerius Diocles who took the name Diocletianus that is commonly abbreviated to Diocletian. His first act as Emperor was to take his sword and kill the praetorian prefect Flavius Aper whom he accused of the murder of Numerian.

In 285 the forces of Diocletian and Carinus met in battle at the Margus River in Moesia (modern Serbia). The battle was going in favour of Carinus when some of his troops mutinied and he was probably murdered by someone on his own side. Diocletian was now undisputed as Emperor.

Despite being unchallenged, Diocletian was wise enough to realise that things were unlikely to stay that way. Past history showed that, with Emperors having to be constantly on the move to defend the frontiers at one point or another, the close relationship between the governing class in Rome and the Emperor’s inner circle was breaking down. Without this communication there was every chance of factions arising that would foment rebellion and civil war. It was impossible to have a mobile Emperor and stable central authority at the same time.

Diocletian therefore took steps to devolve his authority by sharing power on a regional basis. He married one of his daughters to an officer called Maximian who was then made Augustus with dominion over the western provinces of the Empire, although it was made clear that Diocletian, in the east, would have seniority over him. Two junior Emperors, with the rank of Caesar, were also appointed later on, these being Flavius Constantius and Gaius Galerius. Constantius acted as deputy to Maximian and Galerius worked with Diocletian. The juniors also established a family relationship with their bosses by marrying their daughters. This four-way arrangement is known to historians as the Tetrarchy.

Diocletian also established new power bases for the Empire, with the emphasis being taken away from Rome itself. He established himself at Nicomedia in northwestern Turkey, and only visited Rome twice during his 21 years as Emperor. Other centres were where the Emperor, junior or senior, chose to reside, with palaces being built at Sirmium (Serbia), Aquileia and Milan (northern Italy), and Trier in Germany.

Diocletian went further by subdividing local government into twelve “dioceses”, equally divided between the eastern and western halves of the Empire. Although these enabled power to be devolved away from Rome, they increased the overall bureaucratic burden of running the Empire and also had the long-term effect of weakening its overall cohesion.

Another reform was to create a civil adminstration that was no longer dominated by the super-rich. This had been made easier by the hyperinflation of previous reigns, so that the huge fortunes of those at the top were now worth much less, and property valuations that had previously defined the class structure were now meaningless. It was therefore possible for people of relatively modest means to gain high office.

Reforms were also made to the legal and taxation systems, and Diocletian tried to institute economic stability through an “Edict on Maximum Prices”, although this proved to be a failure because it ignored some of the basic laws of supply and demand.

Despite his well-deserved reputation for clemency and humanity, Diocletian was not above persecuting Christians. In February 303 he issued an Empire-wide edict that ordered all Christians to sacrifice to the traditional gods, with severe punishments threatened for those who disobeyed. However, the tetrachs differed in their application of the edict, which ceased to be enforced after about 18 months. It was in any case becoming very difficult to enforce such edicts in a world where Christians had infiltrated institutions including the army, the imperial court and higher education.

In 305, having reached the age of 60, Diocletian decided to retire. His plan was that he and Maximian would retire at the same time, leaving the junior emperors to step into their shoes and appointing two new men as Caesars (Maximinus Daia and Flavius Valerius Severus). Maximian was not overjoyed at the idea, but he had no choice. At a ceremony on 1st May the two senior emperors abdicated.

Diocletian retired to a palace in his native Dalmatia where he enjoyed his later years growing vegetables in his garden, but he was to be called upon again to settle the power balance of the Empire.

Diocletian’s legacy should have been a degree of stability that the Empire had not known for a long time. However, despite the apparent elements of devolution, the arrangements under the Tetrarchy still depended on each member conceding that the ultimate decision-making power lay with one man. Once that man had gone, it was open season again for ambitious men to grab as much power as they could.

Galerius found that he did not have the authority of Diocletian to assert himself over other claimants, notably Maxentius who was the son of Maximian, who in July 306 came out of retirement to support his son’s claim to be Emperor after Constantius’s son, Constantine, had been declared Emperor on the death of his father. Galerius called on Diocletian to come to his aid.

Diocletian presided over a conference at which Galerius ended up being recognised by all parties as the senior Emperor. However, there was no guarantee that future trouble of a similar kind could be avoided without bloodshed, and this was indeed what was in store in later years.

Diocletian died in 313 (this is not certain, it could have been earlier) at the age (probably) of 68.

© John Welford