On October 28, 312, Constantine I defeats Maxentius during the Battle of the Milvian Bridge. The result of the battle over a key crossing over the Tiber included the death of Maxentius (one of the claimants to power over the Roman Empire) due to drowning, the eventual end to the Tetrarchy (in which rule over the Roman Empire was divided between four figures), and the rise and spread of Christendom. Constantine ultimately united the Eastern and Western Roman Empires in 324 with the defeat of Licinius in the East and Constantine become the sole ruler of Rome.

One the most important elements of the Battle of the Milvian Bridge is its significance in the rise of Christianity. According to certain accounts, Constantine had received a divine vision telling him that if he marched under the sign of Christianity he would win the battle. Constantine then had the Chi Rho (an early Christian symbol shown on the shield pictured) painted onto the shields of his soldiers. This is considered to be one of the earliest signs of Constantine's conversion to Christianity and the issuance of the Edict of Milan, legalizing Christianity within the Roman Empire.