Constantine is known for being the first Roman emperor to accept and promote the Christian religion and was largely responsible for how prominent it became during the Middle Ages. He also established a new Roman capital he called New Rome, or Constantinople, as it was commonly called by his subjects, in an old Greek town previously called Byzantium.
The emperor before Constantine harshly persecuted people of the Christian faith. In 313, Constantine issued the Edict of Milan, which gave all people the freedom to choose their own religion. This interest in religious doctrine set a new standard for emperors to come. Numerous irreversible cultural issues arose from this new way of life, as many of Rome's civic events were based on secret religious rituals. Previously, Christianity was viewed as a cult. Suddenly Christians were offered government jobs and were favored by an emperor.
Constantine also hastened the decline of the once-great city of Rome by establishing a competing capital in the East. In 286, Diocletian had moved the Roman capital to what later became Milan, which weakened the city of Rome. However, the capital still remained in Italy, in Roman territories. Constantine's decision to establish a new Roman capital to celebrate a victory in war played a major role in the weakening of the city of Rome.