According to tradition, on the eve of the decisive battle at the Milvian Bridge in 312, Constantine saw a sign in the sky and ordered it to be painted on his soldiers' shields. Victory over his rival made him master of the western part of the empire. Whatever lies behind this account, it was from that moment on that Christianity and Constantine's power moved side by side.
Already in 313 the Edict of Milan, issued jointly with Licinius, proclaimed religious tolerance and ended the persecutions: Christianity passed from a persecuted faith to a permitted one. Confiscated property was returned to the churches, and yesterday's martyrs became subjects protected by law. For the first time in three centuries, to confess Christ ceased to be mortally dangerous.
In 325 Constantine convened the First Ecumenical Council at Nicaea to end the dispute over the nature of Christ. The Council condemned the teaching of Arius and laid the foundation of the Creed — the short confession of faith that is still recited at worship today. The emperor, not yet baptized, presided among the bishops: the spiritual and the political were bound together in a single knot. He also founded a new capital on the Bosphorus — Constantinople, the "New Rome," the center of a future Christian empire for a thousand years.
And here the ambiguity is born. Freedom turned into an alliance with the state: a faith persecuted yesterday began to lean on the sword and the treasury. From this comes both the grandeur of Christian civilization and its perpetual temptation — "imperial Christianity," in which it is hard to tell service to God from service to the state.