First of two episodes.
In October 312, Roman Emperors Constantine I and Maxentius clashed at the Battle of Milvian Bridge to decide who would become the sole ruler of the Roman Empire. Prior to the battle, Constantine reportedly has a vision of a Christian symbol and the message "under this sign conquer". Eventually, Constantine would make Christianity the "official" religion of the Empire.
How would things have differed if Constantine had not led this change?