The Arch of Constantine is the largest and most recent Roman triumphal arch left standing. It commemorates Constantine’s victory over Roman Emperor Maxentius in AD 312 at the Battle of the Milvian Bridge. Why were Romans fighting Romans, you ask? Well, civil war wasn’t new to Rome, look up Julius Caesar and Pompey’s Battle of Pharsalus, or Octavian and Marc Antony’s Battle of Actium. It was all about the power.
This particular civil war goes back to around AD 285 when Emperor Diocletian made Maximian co-emperor, which meant Rome was split into two parts, each with its own emperor and military. Then a few years later he appointed two more junior emperors; Galerius, who was married to his daughter, and Constantius, who was forced to divorce his wife and marry the step-daughter of Maximian. This meant the Empire was divided into four parts, with the two junior emperors being loyal to the senior emperors because they were married to their daughters. Interesting fact here, the two senior emperors had the title Augustus, while the junior ones received the title Caesar. This was called a Tetrarchy, which meant ‘rule of four’. I believe the reason for this division of the rule over the Roman Empire was because the Empire was huge at this point, so joint rule was necessary to be able to better fight the barbarian enemies on all the borders of Rome.
The sons of the rulers were brought up in Diocletian’s court, sort of as hostages to ensure their fathers didn’t rebel. This included Constantine (the son of Constantius), who witnessed Diocletian’s persecution of the Christians, when he published an edict forbidding Christians to assemble for worship and ordering all Christian scriptures to be destroyed.
Diocletian and Maximian both decided to retire in AD 305, which meant Constantius and Galerius both became the senior emperors. The big problem was that Galerius ignored his son-in-law Maxentius and Constantius’ son Constantine who both should have inherited positions in the Tetrarchy. Galerius appointed his nephew Maximinus II and made Constantine appoint Severus, who was Galerius’ man. The fact that Galerius decided to overlook both of the emperor’s sons made the army very angry. Constantine knew he would be in danger staying in the court of Galerius in the east, so he fled to his father in the west. When Constantius died in AD 306, the army proclaimed his son Constantine as emperor, which Galerius didn’t have much choice but to accept.
While this was going on, Maxentius, the son of the original co-emperor Maximian (the guy who was initially ruling alongside Diocletian), decided he wanted to rule too. Of interest, Maxentius was married to the daughter of the current emperor Galerius. So, Maxentius promised money to the army and they proclaimed him emperor also, which meant there was a fifth emperor who was not accepted by the others. So began civil war, with Maxentius defeating the Emperor Severus, by bribing his soldiers to switch sides. He did the same thing with the army of Galerius. He was a very unpopular ruler, known to be particularly ruthless and not true to his promises.
So, the civil war continued, with fighting between the emperors. Another emperor, Licinius, was appointed and Galerius died some time later. Another interesting point here is that Maxentius and Constantine were brothers-in-law because Constantine was married to the sister of Maxentius. Eventually it came down to a big battle between the army of Constantine and the army of Maxentius in the western part of the Empire where Maxentius had control over Italy. The Romans were very superstitious and would often look for signs in the flight patterns of birds or have entrails read before big battles. This is the moment where Constantine claimed to see the Chi-Ro symbol above the sun and ordered his soldiers to paint that symbol on their shields. From then on, he saw himself as a Christian Emperor. It is said that Maxentius consulted the Sibylline Oracles and was told that ‘an enemy of Rome would die’. So, instead of staying and defending Rome like he should have, Maxentius went out to face Constantine at the Milvian Bridge. So, it was here that Constantine fought against the much larger forces of Maxentius. Constantine pushed Maxentius and his army back towards the Tiber and they tried to flee back across the river, but Maxentius was weighed down by his armour and died. This gave Constantine control of half of the Roman Empire.
So that was what the Arch of Constantine was all about. The battle where Constantine took the power over Italy from Maxentius by engaging in civil war at the Battle of the Milvian Bridge, and also where he converted to Christianity and became Rome’s first Christian Emperor.
Of course, the story doesn’t end there, and none of Rome’s Emperor stories seem to have happy endings. The other half of the Empire was under the control of Licinius. In order to make an alliance, Licinius married Constantine’s sister. They also issued the Edict of Milan in AD 313 which was the one that made things so much better for the Christians. But of course their alliance didn’t last long. Constantine and Licinius started fighting for the power again a few years later, so Rome went back to civil war again, until Constantine eventually conquered the entire Roman Empire. As Obelix would say, ‘these Romans are crazy!’
The Arch itself is actually a triple arch, with the big one in the middle and two smaller arches on each side. Apparently there is some controversy over this arch because a lot of the upper decoration comes from other monuments, but I’ll leave that for you to look up if you’re interested!