Rome: The tetrarchy

Now what?... unrest in the Roman Empire... again. What happened? Well, you might remember that after the five good emperors the Roman Peace - Pax Romana - ended.

Now it's the third century, and there's a crisis. No-one is clearly in line to be emperor. Many want to sit on the emperor's throne, and no one hesitates to kill someone else to get there. But the Roman Empire is actually very, very big. How can the 'emperors' take care of it, and guard its borders, while they are busy fighting among themselves? - They can't!

A number of Germanic tribes invade and plunder the empire's borders. The crisis during the third century does not end, until this emperor's reign: Diocletianus. Diocletianus realises that it's impossible for one ruler to look after the whole empire. And that it must be clearer who follows whom. Diocletianus now changes the entire system of government.

The Empire gets four emperors, ruling together, but responsible for different parts of the empire. First, Diocletianus chooses one co-emperor; Maximianus. The two of them become 'head emperors' - and have the title 'Augustus'. Diocletianus looks after the eastern part of the empire, while Maximianus looks after the western part. Diocletianus and Maximianus each choose a 'junior emperor': Galerius and Constantius.

The title of the 'junior emperor' is 'Caesar'. This form of government with four rulers is called tetrarchy. Rome is still capital of the empire but the emperors don't live there. They live in district capitals, closer to the borders. Diocletianus and the emperors after him differ from the earlier emperors in another important way: They no longer use the title Princeps.

Instead they use a title that means Lord: 'Dominus'. Dominus is the same title slaves use for their owners. This changes the picture of what an emperor is. From being 'princeps', the first in the senate, he is now 'dominus': the Lord over all. That's why this period is called 'the dominate'.

Diocletianus also decides that the head emperors are to willingly pass on their titles to the junior emperors, after a time. This works well at the first transition. Diocletianus and Maximianus retire. Galerius and Constantius rise up one level, and gain new junior emperors. But now the problems start.

This is the son of Constantius: Constantine. And this is the son of Maximianus: Maxentius. Everyone expects these two to succeed their fathers to become junior emperors. But, at the last moment Galerius appoints two men close to him: Maximinus Daia and Severus. Both Constantine and Maxentius are disappointed of course.

Only one year later, Constantius dies and Galerius appoints Severus as the new Augustus. And that's when the real mess begins: The army of Constantius still believes Constantine to be the heir of his father. So they appoint him as their Augustus. Meanwhile Maxentius is still annoyed, and wants to get in on the game, so he fights Severus. He murders him and proclaims himself 'Augustus'.

Then Maxentius' father, Maximianus - who already retired once - returns to co-rule with Maxentius. Also as 'Augustus'. This means that suddenly there are five emperors. Four who go by the title of Augustus and only one as Caesar. The Tetrarchy is breaking down.

Years of fighting follow, and finally there are two emperors left. Constantine in the west, and this fellow, Licinius in the east. Is the mess over now? No, Licinius goes after Constantine. But loses.

Now there is only one emperor left to rule the whole empire. Constantine. Or Constantine the Great as he is also called.