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Gaius Aurelius Valerius Diocletianus (ca.245-313), Roman Emperor Diocletian. Marble bust, XVIIth century, Florence, Italy. On display at Château de Vaux-le-Vicomte, France.

Emperor Diocletian: The Stabilizer of Rome Had a Green Thumb


Diocletian was a Roman emperor who lived between the 3rd and 4th centuries AD. Prior to his ascension to the throne, the Roman Empire was going through the Crisis of the Third Century, a period during which the empire was in turmoil, and was on the brink of collapse. When Diocletian came to power, he instituted reforms that not only stabilized the empire, but also had an impact on the shape of the Roman Empire for centuries to come.

The Mystery of Diocletian’s Family

Diocletian (born Diocles and with a full name, as recorded in official inscriptions, of Gaius Aurelius Valerius Diocletianus) was born in 245 AD at Dioclea, near Salona, in Dalmatia (in modern day Croatia). Little is known about his origins. His mother’s name, for instance, has been lost to history, whilst his father is said to have been a scribe or an emancipated slave of a senator by the name of Anullinus. Diocletian was a military man, rising through the ranks until he attained the position of commander of Emperor Carus’ bodyguards.

Diocletian's camp and Qasr Ibn Maʿan. (Ulrich Waack/CC BY SA 3.0)

Diocletian's camp and Qasr Ibn Maʿan. (Ulrich Waack/CC BY SA 3.0)

An Empire Divided

In 283 AD, Carus died, and his two sons, Carinus and Numerian, ruled the empire as co-emperors. Numerian died in the east in 284 AD, allegedly murdered by his Praetorian Prefect, Arrius Aper. Diocletian was proclaimed as emperor by Numerian’s troops, and the new emperor slew Aper with his own hands. Apparently, there was a prophecy stating that Diocletian would become the Roman emperor on the day he killed a boar (which in Latin is ‘aper’).

Diocletian’s power, however, was limited to the areas controlled by his army, i.e. Asia Minor, and possibly Syria. The rest of the empire was still loyal to Carinus, Numerian’s brother. A war between the two men was inevitable. Carinus first defeated Julianus, an army commander in Pannonia who had revolted, before proceeding to deal with Diocletian. In 285 AD, the Battle of the Margus was fought between Carinus and Diocletian’s armies. Initially, it seemed that Carinus was winning. The tide changed, however, when Aristobulus, the Praetorian Prefect of Carinus, defected, and Carinus himself was assassinated. As a consequence of Carinus’ death, Diocletian became the sole ruler of the Roman Empire.

Realizing that the empire was too large for him to rule on his own, Diocletian decided to divide the empire between himself and a colleague of his choice. Thus, in 286 AD, Maximian, one of Diocletian’s old comrades, was proclaimed co-emperor. Whilst Diocletian ruled in the east, Maximian was in charge of the west. In 293 AD, each emperor appointed a caesar of his choice, who would take over as emperor in the event of their deaths. Thus, the Tetrarchy (meaning ‘rule of four’) was established in the Roman Empire.

Small bronze coin (denarius?) of Maximianus Herculius. (Aaron Bruce/CC BY SA 3.0)

Small bronze coin (denarius?) of Maximianus Herculius. (Aaron Bruce/CC BY SA 3.0)

The Diocletian Tetrarchy

Diocletian’s institution of the Tetrarchy was meant to counter a problem that had been prevalent during the Crisis of the Third Century. During this chaotic period, emperor assassinations were common. The death of an emperor was often followed by a period of war between factions trying to claim power. This in turn contributed to the instability of the empire. With the establishment of the Tetrarchy, the Roman Empire was made more stable. The death one Tetrarch would not result in the same kind of power vacuum caused by the death of a sole emperor.

The Tetrarchy worked well during Diocletian’s lifetime, though it began to fall apart not long after his death, as a consequence of the conflict that arose amongst his successors. Although the Tetrarchy ended with the re-unification of the Roman Empire under Constantine, it marked the beginning of the empire’s division into the Eastern and Western Roman Empires.

Laureate head of Diocletian. (G.dallorto)

Laureate head of Diocletian. (G.dallorto)

Diocletian’s Persecution of Christians

Diocletian also has a place in the history of Christianity, where he is remembered as a persecutor of the Church. Whilst Christianity was allowed to exist peacefully during the early part of Diocletian’s reign, the Diocletianic Persecution took place in the last years of the emperor’s life. It is unclear what triggered the persecution, but it spread across the empire with violence. Instead of destroying the Christian faith, however, the persecution strengthened the Church.

Diocletian abdicated in 305 AD, and was succeeded by his caesar, Galerius. He retired to his palace at Split (in modern day Croatia), where he apparently spent his time gardening. When Maximian wrote to him suggesting that he ought to return to politics, Diocletian allegedly replied that if he were to see the cabbages grown in his garden, he would understand the impossibility of this suggestion. Diocletian died in 313 AD.

Diocletian in retirement. (Public Domain)

Diocletian in retirement. (Public Domain)

Top Image: Gaius Aurelius Valerius Diocletianus (ca.245-313), Roman Emperor Diocletian. Marble bust, XVIIth century, Florence, Italy. On display at Château de Vaux-le-Vicomte, France. Source: Public Domain

By Wu Mingren


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Wu Mingren (‘Dhwty’) has a Bachelor of Arts in Ancient History and Archaeology. Although his primary interest is in the ancient civilizations of the Near East, he is also interested in other geographical regions, as well as other time periods.... Read More

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