The Start of the Byzantine Empire: The History of the Eastern Roman Empire's Establishment as Roman

It would be hard if not outright impossible to overstate the impact Roman Emperor Constantine I had on the history of Christianity, ancient Rome, and Europe as a whole. Best known as Constantine the Great, the kind of moniker only earned by rulers who have distinguished themselves in battle and conquest, Constantine remains an influential and controversial figure to this day. He achieved enduring fame by being the first Roman emperor to personally convert to Christianity, and for his notorious Edict of Milan, the imperial decree which legalized the worship of Christ and promoted religious freedom throughout the Empire. More than 1500 years after Constantine's death, Abdu'l-Bahá, the head of the Bahá'í Faith, wrote, "His blessed name shines out across the dawn of history like the morning star, and his rank and fame among the world's noblest and most highly civilized is still on the tongues of Christians of all denominations"
However, it can be argued that despite his military successes – the most notable of which occurred fighting for supremacy against other Romans – Constantine may well have set the stage for the ultimate collapse of the Roman Empire as it had existed up until that point. It was Constantine who first decided that Rome, exposed and vulnerable near the gathering masses of barbarians moving into Germania and Gaul, was a strategically unsafe base for the Empire, and thus expanded the city of New Rome on the Dardanelles straits, creating what eventually became Constantinople. By moving the political, administrative and military capital of the Empire from Rome to the East, as well as the Imperial court with all its attendant followers, Constantine laid the groundwork for the eventual schism which saw the two parts of the Roman Empire become two entirely separate entities, go their own way, and eventually collapse piecemeal under repeated waves of invasion.