In the early Roman Empire, as Christianity struggled to gain a foothold and survive in the polytheistic pool of Roman theology, its greatest rivals weren't the Caesars or the Roman aristocracy but rather the faith and devotion of the common Roman legionary. The faith of these men was centered on the god Mithras, who, they believed, led them to victory upon the field of battle and had done so for nearly four centuries.

Despite this widespread belief among soldiers, the cult of Mithras was not a creation of the Romans, although they would eventually add their own rituals and mysteries to the ancient religion. In fact, the Mithraic religion was an Indo-Persian creation, a theology which managed to travel from India and back into the Hellenic and Roman world by way of Alexander the Great's conquest of the Persian Empire. Eventually, the cult of Mithras would spread across the ancient world, and Mithras would be worshiped from the mountains of India to the coasts of Spain. As a result, the cult of Mithras could ultimately be found in every corner of the Roman Empire.