9The sun god Mithra was worshiped extensively in pre-Zoroastrian Persia; at the height of the Roman Empire, during the second and third centuries, he was venerated as Mithras, Deus Sol Invictus ("The Unconquered Sun God"). The emperors of Ancient Rome ascribed the success of imperial Persia - which they failed to subdue - to the latter's belief in Mithras. Hence the Romans adopted Mithras themselves, believing him to be key to acquiring such invincibility. Thus the cult of the sun god became a full state religion. For over four hundred years, Mithras was revered by emperors, governors, procurators, commanding generals, legionaries and centurions all across Roman Europe, and many Mithraic temples were built in his name. Elite Mithraists were initiated into special rites and ceremonies - called the Mysteries - by Mithraic high priests. A major competitor to early Christianity within the Roman Empire, Mithraism saw many of its rites and doctrines adopted by the Church, and many a Christian church would be erected on the site of a former Mithraeum. Extensively illustrated and researched, Deus Sol Invictus reaches back into the earliest Persian origins of Mithraism until the last vestiges of the religion in Rome, and provides exquisite detail on every facet of this once-pervasive belief system.