Diocletianus: The Years 284-293

Head of Carinus (Centrale Montemartini, Rome).

In the year 284 the Roman Empire had two augusti, who were not on speaking terms. Of the two, Carinus was the legitimate emperor. Immediately after the death of his father Carus in the summer of 283 he had travelled to Rome to claim the purple. For about a year he ruled together with his brother Numerianus, who had accompanied Carus on his campaign against the Persians. Towards the end of 284 Numerianus had died under mysterious circumstances, after which a council of generals and military tribunes had proclaimed Gaius Aurelius Valerius Diocles augustus. Diocles, commander of the imperial bodyguard, would quickly change his name to Diocletianus. He would go on to sit on the imperial throne for a grand total of 21 years and can be counted among the most important Roman emperors of the third century. He was nevertheless a controversial figure. Diocletianus was generally praised for his political and economic reforms, although these did not always have the desired effect. On the other hand, the emperor is also remembered as a fanatical persecutor of Christians. He was the instigator of the last great persecution of Christians in the Roman Empire.

Diocletianus assumes power

Most of our sources are extremely negative about Carinus. All sorts of misconduct are attributed to him, ranging from adultery to murder, and from nepotism to spendthrift. It may be doubted whether it was really all that bad, but then again history is not written by the losing side. Carinus, in any case, seems to have been a capable general. He had previously won victories against Germanic tribes along the Rhine and now managed to successfully deal with one Marcus Aurelius Sabinus Julianus. It is not entirely clear who this Julianus was. It is possible that he was the governor of the region Venetia et Histria, and he certainly had troops under his command, as he succeeded in capturing the mint in Siscia in Pannonia (now Sisak in Croatia). Julianus must have had plans to march on Rome and have himself recognised as the legitimate augustus there, as in the Spring of 285 his army and that of Carinus clashed, possibly in the vicinity of Verona. Carinus won an easy victory and now prepared himself for a confrontation with Diocletianus.

The struggle for control of the Roman Empire was ultimately decided at the river Margus, nowadays the Morava in Serbia. Somewhere between April and the early Summer, the two armies presumably bumped into each other near Viminacium, the capital of Moesia Superior and the headquarters of Legio VII Claudia. Carinus had every reason to be optimistic about the outcome of the battle. His legions, raised in the Rhine and Danube provinces, were considered superior to the Syrian legions under the command of Diocletianus. Moreover, according to Eutropius, Carinus’ army was larger than that of his opponent. His troops began pushing back those of Diocletianus, but in the end Carinus was murdered by one of his own military tribunes. The emperor had supposedly seduced the man’s wife. The story sounds like a fabrication, and it is much more likely that Diocletianus had simply struck a deal with Titus Claudius Aurelius Aristobulus. This Aristobulus was serving as praetorian prefect under Carinus and had held the consulship with him in 285. Diocletianus would later richly reward Aristobulus for his support. After a governorship in the province of Africa, the man ended his career as praefectus urbi in Rome.

Statue of Maximianus (Rijksmuseum van Oudheden, Leiden).

After Carinus’ death his troops quickly surrendered. Diocletianus declared a general amnesty, and for a brief period ruled as sole augustus over the immense Roman Empire. His predecessors had all appointed one of more co-emperors and Diocletianus would soon do the same. There was a serious problem though. The emperor did not have a son or brother, only a daughter called Valeria. The emperor, himself a lowborn Dalmatian, therefore at some point in 285 (possibly in June or July) decided to appoint a certain Maximianus as his caesar. Maximianus had been born in the vicinity of Sirmium (modern Sremska Mitrovica in Serbia). The two men had met while serving in the army and Diocletianus seems to have had blind faith in his caesar. Not much later, on 1 April 286, Maximianus was promoted to augustus. The Roman Empire now had two emperors, but the two were not equals. Diocletianus took the title of Jovius as a demonstration of his devotion to Jupiter, the supreme god of the Romans. Maximianus in his turn became Herculius. The latter title was not just an indication of the emperor’s devotion to Hercules, but also proof of his subservience to Diocletianus. After all, in the Roman Pantheon, Jupiter clearly ranked above Hercules, who was his son by a mortal woman. Maximianus would never forget to whom he owed his imperial throne.

Diocletianus’ power grab marks the end of the Principate and the transition to the Dominate. Instead of princeps civitatis, first citizen of the State, the emperor had now become dominus et deus, lord and god. It should be noted that emperor worship (adoratio) was already quite common in the Roman Empire, especially in the Greek-speaking east. Moreover, a couple of previous emperors had also styled themselves dominus et deus. It follows that the establishment of the Dominate, with the emperor ostentatiously dressing up as a living deity, was a final step in a gradual process rather than a big bang. Nevertheless, it was an important step, which went hand in hand with the emperor-god being secluded from the public, the obligation for visitors to prostrate themselves before him and an extensive court ceremonial full of pomp and extravagance.

Campaigns in 286-288

Remains of the palace of Maximianus in Milan (Via Brisa).

Although Diocletianus and Maximianus brought peace and stability to the Empire, they also campaigned incessantly along the Empire’s borders. Maximianus’ first assignment was the fight against the Bagaudae in Gaul. The Bagaudae were bands of extremely dangerous brigands who terrorised the countryside and even threatened cities. They were led by former soldiers and were therefore able to operate effectively. Their situation being rather desperate – the Bagaudae were often farmers without land and other poor –, they knew that they had little to lose. Maximianus nevertheless managed to deal with the brigands fairly quickly and extremely harshly. He then marched to Augusta Treverorum (Trier), which he would use as a base for future operations. Together with Mediolanum (Milan), Augusta Treverorum would become the de facto capital of Maximianus’ part of the Roman Empire. Diocletianus would ultimately settle in Nicomedia in Bithynia, the place where he had been proclaimed emperor.

After defeating the Bagaudae, Maximianus focused on combating piracy in the British Channel, where Frankish, Saxon and Frisian marauders wreaked havoc. Around 287 he had equipped a fleet, the new Classis Britannica, and was preparing to exterminate the pirates. Part of the process was the construction of a line of fortresses along the British east coast, between Portus Adurni (Portchester) and Branodunum (Brancaster). These defensive works are collectively known as the litus Saxonicum or ‘Saxon coast’. Their principal purpose was to defend British territory against raids. It is quite possible that most of these activities are to be attributed to a certain Marcus Aurelius Carausius. He was a Roman Celt who was a member of the tribe of the Menapii in present-day Belgium. Carausius knew the British Channel and the North Sea like the back of his hand, which made him the right man for the job of leading the fight against the pirates. He made his headquarters at Gesoriacum (Boulogne), where the Classis Britannica had its base.

Unfortunately things ended badly for Carausius. Although he successfully dealt with the pirates, his detractors claimed that he kept most of the loot for himself. When word about this reached Maximianus, he immediately ordered the execution of his fleet commander. Carausius fled to Britannia head-over-heels, where he had the provincial governors murdered and quickly won over the army. Next he proclaimed himself emperor. This was a huge setback for Maximianus, who had not only lost control of Britannia for the moment, but also had to watch helplessly how it was Carausius who was calling the shots in and around Gesoriacum. The Celt may even have been in effective control of Rotomagus (Rouen) and its mint. On the other hand, Carausius’ intentions do not seem to have been hostile. He tried to win the friendship of Maximianus and Diocletianus and sought to be recognised by them as brother (frater) and co-emperor. In any case, he never attempted to invade the territories of the former or depose him. Unfortunately Carausius’ love for the other two was never reciprocated.

In the meantime Maximianus won a couple of successes on other fronts. He defeated a string of Germanic tribes, with various sources mentioning the Alemanni, Burgundi, Franks, Heruli and the rather obscure Chaibones. There must have been several campaigns in several years, but in spite of the Roman victories the Germanic threat did not disappear. Around the year 288 a certain Flavius Valerius Constantius appears on the stage for the first time. Today he is more widely known as Constantius Chlorus, ‘the Pale’. Constantius had been born in Naissus (modern Niš in Serbia), so like Maximianus he was a child of the Balkans. As a general and possibly praetorian prefect under Maximianus he was involved in a campaign that led to the subjugation of the Frankish king Gennobaudes. Presumably many of Maximianus’ successes on the battlefield were in fact achieved by Constantius. The emperor showed his gratitude by offering his general the hand of his stepdaughter Theodora. She was the daughter of Maximianus’ wife Eutropia and her first husband Hannibalianus. It is highly likely that both Theodora (‘gift of God’) and her mother (a Syrian) were Christians.[1] Constantius and Theodora were duly married and she bore her husband six children. One of these, a daughter, was named Anastasia, a name that refers to the anastasis or resurrection of Christ.

Head of Constantius Chlorus (Vatican Museums).

Constantius and Theodora were probably joined in a mixed pagan-Christian marriage, with the children receiving Christian names and being raised – at least partially – as Christians. In order to marry Theodora, Constantius had to cancel his relationship with a certain Helena. She was from the region around Nicomedia and had probably been born in the town of Drepanon (later renamed Helenopolis). Later sources claim she was the daughter of an innkeeper. Zosimus even more or less states that she was a prostitute, writing that Constantine was born ἐξ ἀσέμνου μητρὸς, from an ‘obscene mother’.[2] Helena’s native language was Greek and tradition dictates that she was a Christian as well, which is quite plausible given the strong presence of the Christian religion in and around Nicomedia. Given the class difference between the two, it is far from certain whether Constantius and Helena ever formally married. However, there can be no doubt that their relationship involved sexual intercourse, as around 272 a son was born in Naissus. Even today people still remember his name: Flavius Valerius Constantinus, the future emperor Constantine the Great (306-337).

Campaigns in 289-293

The continued occupation of Gesoriacum by Carausius was like a bone stuck in Maximianus’ throat. In 289 he attacked the city with an army and fleet. The Menapian, however, easily defeated the imperial fleet, leaving it to be finished by a terrible storm. With the fleet lost, Maximianus’s army was forced to break off the siege of Gesoriacum. Events in North Africa now demanded the emperor’s attention. Berber tribes that are called the Quinquegentiani in the sources – ‘they of the five tribes’ – had invaded Roman territory here. Their attack led to, among other things, the permanent loss of the Roman city of Volubilis in present-day Morocco.

In the meantime Diocletianus had successfully concluded several campaigns along the Danube (ca. 286-289). He could now focus on the east, where trouble had arisen in Armenia. The Armenian kingdom was of great strategic importance and had been an eternal bone of contention between Rome and the Persian Sassanids. Ever since the murder of the Armenian king Khosrov II around the year 252, Armenia had been occupied by the Persians. Back then, Khosrov’s young son Tiridates had been smuggled out of the country and was now, almost forty years later, living in Roman territory. Diocletianus was waiting for the right moment to get him back on his father’s throne. For now, diplomacy was his most important weapon, as the Persian king Bahram II was very anxious to prevent a new war with the Romans. After all, he had lost big in the previous war with Carus. Diocletianus and the king ultimately reached an agreement, which led to the latter ceding some territory to Rome. It is not clear what exactly had been agreed. Most likely parts of Mesopotamia were returned to Roman control, although it had been suggested that part of Armenia was given back to Tiridates, while Narses, Bahram’s uncle, continued to rule the rest of Armenia. However, there is no compelling evidence for this assumption.

In 290, after the agreement with the Sassanids, Diocletianus could focus on the Arab raiders that had invaded Roman territory from the Sinai desert. In 291 he subsequently marched to Egypt, which had seen another invasion of the nomadic Blemmyes. Now the tribesmen had occupied part of the province. The Nubian Blemmyes had previously given the emperor Probus (276-282) a headache, but Diocletianus managed to push them back to Philae at the first cataract of the Nile and then concluded a peace treaty with them and their allies, the Nobatae. The next year, in 292, the emperor was back on the Danube, fighting the Sarmatians. Diocletianus basically had to be everywhere at the same time, but in practice this was utterly impossible. His co-emperor Maximianus was faced with the same problem. Constantly being on the move and constantly fighting wars on many different fronts must have contributed to Diocletianus’ decision in 293 to introduce a new system of government, the Tetrarchy. The Tetrarchy will be discussed extensively in the next post.


Primary sources

Secondary sources

  • Adrian Goldsworthy, The Fall of the West, p. 134-135 and p. 157-160;
  • Henk Singor, Constantijn, p. 136-142;
  • Timothy Venning, A Chronology of the Roman Empire, p. 625-629.


[1] Henk Singor, Constantijn, p. 141; Eusebius, Vita Constantini, Book 3.52.

[2] Zosimus, Historia Nova, Book 2.8. Eutropius (10.2) claims that Constantine was born ex obscuriore matrimonio, ‘from an obscure marriage’. In the Origo Constantini Imperatoris (ca. 390), Constantine is said to have been natus Helena matre vilissima. The word vilis means both ‘cheap’ and ‘poor’ or ‘worthless’. It follows that, according to this source, Helena was of extremely low birth.

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