Emperor Diocletian is probably most famous for the system of government he devised to turn rivals into associates. His system of Tetrarchy was an effective one that helped stabilize the empire and saved it from its seemingly inevitable fall. But after his retirement, things did not go quite as planned.
A New Rival for the Tetrarchs
Diocletian’s two senior emperors, or Augusti, were Constantius Chlorus in the west, and Galerius in the east. Their respective Caesars were Flavius Severus in the west, and Maximinus Daia in the east. After Diocletian retired himself, these Tetrarchs began to develop resentment toward each other. There was also a fifth rival, who made the situation even worse. He was Constantine, the son of Constantius Chlorus, who had been excluded from the Tetrarchy. He was a good general and popular with the western troops. So, after the death of his father in 306 A.D., Constantine was acclaimed as the emperor by the soldiers in Britain.
To avoid an open conflict as a result of this unexpected development, Severus agreed to become the Augustus in the west, and Constantine became his Caesar. Now, another player entered the scene: Maxentius, the son of Maximian, one of the original Tetrarchs. He believed that he should have been chosen over Constantine as his father was the very first Tetrarch chosen by Diocletian. He had the support of an audience as well as the Praetorian Guard in Rome, so he declared himself an emperor, which raged another series of civil wars.
Maxentius had Severus murdered, simple-mindedly thinking he would replace him. But, Galerius, as the most senior emperor, decided to replace Severus with one of his friends, Licinius. So, there were now five emperors who were competing against each other, everyone being angry at others. But the conflicts temporarily paused when the rivals changed their strategies.
Two sets of alliances were formed: Constantine and Licinius on one side and Maximinus Daia and Maxentius on the other. Galerius was trying to keep peace and prevent the empire from falling apart. With his death due to natural causes in 311 A.D., the contenders began their war.
Learn more about gods of the Roman State.
Constantine Converts to Christianity
In 312 A.D., Constantine took on Maxentius and attacked his stronghold in Italy with an army of about 40,000 soldiers. Instead of keeping war inside Rome’s mighty fortifications, Maxentius decided to take the war near the Milvian Bridge.
Before going to this battle, Constantine made a move that no one had done before: he converted to Christianity. Christian authors have provided two descriptions of how this happened.
According to Lactantius, Constantine’s advisor, on the night before the battle, Constantine had a dream in which the Christian god told him to have a Christian logo painted on the soldiers’ shields in the next day’s battle. The symbol is the Chi-Rho, which was the two letters of Christ’s name in Greek overlapped.
Another account was given by the author Eusebius. The day before the battle, the Chi-Rho symbol was superimposed over the sun, as well as the words “in this sign conquer”. Later that night, Constantine saw Jesus in his dream. He said Constantine and his soldiers would beat Maxentius if they carried the Chi-Rho symbol into the battle. So they did, and they won the battle, heartened by the thought that a god had their back.
This is a transcript from the video series The Roman Empire: From Augustus to the Fall of Rome. Watch it now, on Wondrium.
Constantine Becomes the Sole Emperor
After the battle, Maxentius fell into the Tiber River and drowned. After the war, the alliance between Constantine and Licinius was fortified against Maxentius’s former ally, Maximinus Daia. In the Edict of Milan, they announced that all religions would be tolerated, and the confiscated properties would be returned to the Christian Church. To further solidify their alliance, Licinius married Constantine’s half-sister, Constantia.
Maximinus decided to take a preemptive strike as he knew this alliance could not be defeated. He attacked Licinius’s territory, but he was bitterly defeated. Maximinus escaped and soon killed himself. Now the empire was divided between Licinius and Constantine, the former controlling the east and the latter the west. They managed to maintain peace, although the frequently had disputes. However, in 320 A.D., when Licinius started to persecute Christians in his territory, things began to unravel.
The final straw was Constantine’s march into Licinius’s half of the empire in 323 A.D. supposedly to repel a Gothic rebellion. Two battles of Adrianople and Byzantium followed, in which Licinius was defeated. Constantine sent him on exile at Thessalonica but killed him and his son a few months later for charges of treason. As the sole emperor of Rome, Constantine ruled for 13 years. He remained a Christian as an emperor, although Christianity was still unknown when he converted.
Learn more about emperor worship in Rome.
Common Questions about the Rise of Constantine, the First Christian Emperor
Constantine was the son of Constantinus Chlorus, one of the Tetrarchs in Diocletian’s system of Tetrarchy. He eventually became the Roman emperor and converted to Christianity.
The first Christian emperor was Constantine. After he had a dream of Jesus telling him to paint the Chi-Rho symbol on his shield, he won the battle with Maxentius. He then officially declared his conversion to Christianity.
Maxentius was the son of Maximian, one of the original Tetrarchs. He declared himself the emperor of Rome, which raged another series of civil wars. In 312 AD, he was defeated by Constantine.