For the first three centuries the true Church was almost threatened with extinction, as the persecutions of pagan Rome increased in intensity under the reigns of the heathen Emperors from Nero to Diocletian. In 303 AD. Diocletian, determined once and for all to stamp out Christianity, issued a series of edicts, each more severe than the former, in his effort to exterminate Christianity. Christians were martyred by the thousands and the Roman prisons were filled to overflowing with believers and especially Christian ministers. Then a most unexpected event took place. Constantine (the Great) became Emperor of Rome in the early part of the fourth century. During one of the crucial battles for conquest he is supposed to have seen in the sky a flaming cross (at midday) with the words inscribed in Greek: "By this sign conquer." It may have been pure imagination in an hour of desperation, or an optical illusion, but whatever it was he accepted it as word from Heaven that this cross was his key to victory. Accordingly he not only accepted Christianity but also made it the religion of the Roman Empire. The result was the Roman Catholic Church, which is a mixture of about one-third Christianity, one-third Judaism, and one-third paganism. This was the beginning of the union of Church and State. Constantine, however, did not oppose the old pagan worship of Rome; rather, he superimposed Christianity upon these pagan religions, adopting elements in both; and thus, by allowing the pagans to continue their heathen customs, he made it easy for them to adopt Christianity. The result was the Roman Catholic Church, which is a mixture of about one- third Christianity, one-third Judaism, and one-third paganism. The Roman Catholic Church thus pretends to accept most of the cardinal doctrines of Christendom, plus the holy days and priesthood copied from Judaism, and the superstitions and fetishes of paganism with its charms such as holy water, candles, and images.

The church of Christ (that is Christ's church, not a name for the church) technically began at the death of Jesus in about 29-31 AD. The commonly given date for the beginning of the church is the Shavuot (Pentecost) of the same year, when the apostles preached the first gospel sermon and about 3,000 souls were added to the church (Acts 2). This church spread from Jerusalem throughout the area, and after about 15 years the members of the church were given the designation "Christians" (Acts 11:26). Each congregation of the church was independent of all others although they shared a common belief, assembled on the first day of the week (and often on other days), regularly participated in "the Lord's Supper" (possibly weekly), and sometimes shared preachers. They were most notable for a missionary spirit and a willingness to die for their beliefs. During the reign of Constantine as Roman Emperor Christianity was officially recognized and shortly thereafter was made the "official" religion of the empire. By this time the governmental plan of the empire had crept into the church, with some bishops (elders) claiming authority over several congregations. There soon developed three, and later five, "sees" (governmental areas) centered around the largest cities of the empire (Rome, Antioch, Byzantium, Alexandria) and Jerusalem. None had authority over the others. The development of this hierarchical system and the ecumenical councils to make decisions for all the church can fairly be said to be the beginning of the Roman and Orthodox Catholic churches. Over a period of years the Bishop of Rome claimed supreme authority over the other bishops. Other doctrinal issues were involved as well, but in 1054 the Bishop of Rome "excommunicated" the Bishop of Constantinople (Byzantium). Most people give this date as the start of the Eastern Orthodox Church, although it is really a date for the beginning of the Roman Catholic Church being separate from the scriptural government, and therefore the true body, of the church. The Eastern Orthodox faith has remained essentially independent of the western church from that time. The Catholic Church maintained its supremacy in western Europe for several centuries.