Constantine the Great, the first Christian Roman emperor, converted to Christianity after receiving a divine sign before the Battle of the Milvian Bridge. In 313 AD, he issued the Edict of Milan, granting Christians the freedom to practice their faith in the Roman Empire. He further established Constantinople in in 330 AD as a Christian capital, uniting the Eastern and Western regions of the empire. This significant transformation had profound effects on the history of the Roman Empire, influencing its political, cultural, and religious aspects.