Constantine the Great 272-337

Christianity Constantine was the first Roman emperor to support Christianity and become Christian. From the time of Constantine, Christianity became the Roman religion, with a temporary setback when his nephew Julian tried to reinstate the old Roman polytheistic beliefs, which we refer to as paganism. Symbolism Constantine was victorious against Emperor Maxentius at the Milvian Bridge, which was significant for its Christian symbolism.

Tolerance Constantine proclaimed the Edict of Milan, in 313, granting religious freedom to all. This was a departure from previous emperor's persecutions of the Christians.

Building a New Rome Constantine created a new Christian capital for the Roman Empire at Byzantium (named Constantinople for him [and later, Istanbul]). To make "New Rome" a truly alternative capital, he installed a second senate there.

Rome's Decline The once great city of Rome was firmly on a decline in terms of power within the Roman Empire. In 286, Diocletian had moved the capital from Rome and established the capital of the western part of the Roman Empire at what we now call Milan (then, Mediolanum), but at least it was still at the heart of Roman territory, in Italy. This was the city in which Constantine issued that document of religious toleration. Establishing a competing capital in the East put another nail in Rome's figurative coffin.

Loss of Cultural Identity Since its founding, Roman civic events had been linked to religious rituals. The Vestal Virgins, priestesses of the Goddess Hestia, were thought to hold the fortune of Rome in their hands. New cults were started and temples built to the gods to ensure military victories. Religion suffused life. With the acceptance by even the emperor of the foreign cult of the Christians, Rome was doomed to radical, irreversible change.

Loss of Cultural Identity Since its founding, Roman civic events had been linked to religious rituals. The Vestal Virgins, priestesses of the Goddess Hestia, were thought to hold the fortune of Rome in their hands. New cults were started and temples built to the gods to ensure military victories. Religion suffused life. With the acceptance by even the emperor of the foreign cult of the Christians, Rome was doomed to radical, irreversible change.

Source: http://ancienthistory.about.com/cs/people/p/constantine.htm