Timeline Ancient Rome

The Tetrarchy: Temporary Stability Brings Drastic Change

Tetrarchy? Sounds almost like a robot. Or some sort of monster. No?

Maybe. But only if your Ancient Greek is a little rusty. Because if it wasn’t, you would know that the word Tetrarchy  has something to do with the number four. In this case, it means government by a group of four people. 

For approximately 30 years, this was how Rome was ruled: by a group of four. Those who have been studying Roman history know this must have gone really well….

Yeah, right. 

As you might expect, sharing power in Rome, while effective for a brief period, did little to solve the underlying division that was contributing to its decline as a unified empire. The attempt, however, helped lay the path for the future of Rome and her many provinces.

The Rise of Diocletian

The Tetrarchy  was the big idea of a man named Diocletian. He came to rule Rome after Aurelian. This guy had defeated breakaway Roman states and the Barbarians, which ended the prolonged Crisis of the Third Century. 

Sensing it would probably be hard for him to hold onto power all by himself (perhaps because he took the position after forty years of civil war), he decided to get ahead of things by agreeing to share power. He appointed a man named Maximian to be his number two, aka his caesar. 

A few years later, he made him an equal, giving him the title augustus, and he divided the empire in two. Diocletian took the Eastern Roman Empire, and Maximian took the Western Roman Empire. They then went further and divided each half again into half.  Each man chose which one they wanted to govern, and then appointed their own caesar to rule the other. 

So, now the empire was split into four parts, each to be governed by someone separately. The caesars were technically supposed to report to their respective augusti, but they were also free to conduct their own affairs. 

This was their way of saying “Look, we all want to be the emperor, but we can’t. So let’s just take a smaller piece and agree to stop fighting. Okay?”

In the early days, this seemed to work out fine. But there was too much at stake to just sit back. This is Rome we’re talking about!

The Tetrarchy

Division Bring Stability, Reform, and Ambition

Although ultimately short-lived, the Tetrarchy did serve its purpose in that it ended the decades of civil wars that had plagued Rome in the third century. During this time, armies and administrative bureaucracies were reorganized to reflect the new division of the empire. 

This helped make things easier to manage and also helped revitalize life in the wartorn provinces of the west. But it also emboldened each member of the Tetrarchy and ramped up competition between them until the peace and stability their arrangement created no longer existed.  

The Civil Wars of the Tetrarchy 

In 305 AD, Diocletian and Maximian had been in office for 20 years. So, as they had agreed when they took power, they both stepped down from their roles as augusti . Their two caesars, men named Constantius and Galerius, assumed the position as co-leaders of Rome. And as had been agreed, they each appointed a caesar. Constantius chose a man named Valerius Severus and Galerius chose Maximinus Daza.

Everything’s good. No need to start a civil war, right?


Constantius died in 306 AD, just a year after taking office, and it was unclear who should take over. The agreement stipulated it should be Valerius Severus, since he was caesar, but Consantius’ son, Constantine, was thinking, “well, if it’s kind of like a king, and I’m his kid, shouldn’t I be augustus. Not this Valerius guy.”

Turns out quite a few people agreed with him and supported his claim. 

Meanwhile, Maximian’s son, Maxentius, saw all this happening and thought, “Yeah! It should go from father to son. So when my dad retired last year, I should have been made augusti. Not this Maximinus Daza guy.”

Acting on this thought, Maxentius attacks Valerius Severan and eventually captures and executes him. Then, Maximian, seeing the success of his son, decided he wanted back into political life and declared himself augsti. 

A Solution Through Peace?

This had turned into quite a mess. So, Rome’s elite called a council, which included Diocletian, who was retired and simply trying to relax by the pool and catch some sun, to come up with a plan. 

What they designed once again solved the problem only temporarily. 

The first part of their solution was to say that Maximian had to retire. He was supposed to anyway, so this was everyone’s way of saying “it’s time.” The second was that Maxentius was declared a usurper, meaning he was trying to steal power, and so he got nothing. 

Lastly, going forward, the empire would continue to be divided into two. One part, the east, would be ruled by Galerius, who was the originally appointed successor to Maximian. Maximinus Daza, his original caesar, would also retain this position. 

In the west, Constantine would be the caesar under a man named Licinius.  He had been an important man in Galerius’ court and who had spent considerable time ruling over his quarter of the empire.

Constantine’s claim was recognized, but he was not given the position of augustus.

And Then There Were Two

Okay, we’re good, right?

Not so fast. 

Shortly after this was all hashed out, Galerius fell ill and by 311 had to step away from public life. Maximinus Daza was poised to take over, but began forming a friendship with Maxentius. So much for being labeled a usurper. 

Constantine and Licinius, who are already rivals simply by being in this arrangement that tries to make fierce competitors get along, formed an alliance in response. 

Together, they defeat both Maximinus Daza and Maxentius and say “enough with the caesars” and agree to rule Rome jointly, just the two of them. No more of this “rule by four people” thing.

It wouldn’t be long before Constantine moved against Licinius and made himself sole emperor of Rome, and ,at the same time, made sweeping changes across the empire. But for a brief period, the two benefited greatly from their alliance.

Defeating Division within the Empire

Numerous things were driving Rome apart during the third and fourth centuries AD. Increasingly powerful provincial elites, invasions from all across the European border, and, of course, religion. 

Despite the empire’s attempt to squash it out through persecution and genocide, Christianity had been on the rise across the empire. And those who believed in it were willing to fight for it. 

To harness this energy, Constantine teamed up with Licinius to recruit Christians to his side. In 313 AD, they issued a statement that is now known as the Edict of Milan. 

The Edict of Milan and the Influence of Christianity

This proclamation from Constantine and Licinius, which came while they were still struggling with Maximinus Daza and Maxentius for control of Rome, officially recognized Christianity. It gave followers the freedom to practice it without persecution and to recover losses from the war. 

Christianity had been on the rise for the previous 300 years, spreading across both Europe and Asia. But Roman emperors, fearing it as a threat to their power, waged war against Christians, crucifying them and persecuting them at every chance they got. 

It did not work. Christianity continued to grow and conflicts between Christians and pagans, those practicing traditional Roman religions, added to the unrest within Roman society.

Constantine, wisely, figured “if you can’t beat ‘em, join ‘em” and welcomed Christians into the empire as equals. This helped him win the support of many of the people living under Roman rule and solidified the claim he was making to be the sole emperor of Rome.

While most certainly politically motivated and meant to help him win his wars, this Edict helped enshrine Constantine as a hero in the Christian religion.

The Importance of the Army

The rise and the fall of the Tetrarchy serves as an important reminder to the importance of military power in ancient Rome. 

The one who got to be emperor was the one who was best at getting men to fight for him. Without soldiers on the battlefield to challenge his contenders, his words were meaningless. 

According to the agreement made between Dicocletian and the original members of the Tetrarchy, Constantine had no “legitimate” claim to power. Yet the soldiers he commanded thought he did, and so did the Christians he agreed to support. So, through force, his claim became legitimate. 

Although the idea of the Tetrarchy may have made sense at the time, it proved impossible to shrink the ambition of its leaders. But its impact goes even deeper. It further divided the Roman empire, and it made it harder than ever to keep it together.

Written by Matthew Jones

Illustrated by Jean Galvao