My sources are Wikipedia and ‘The World’s Religions’, by Peter Clarke, Reader’s Digest Books, 1993.
The New Testament of the Bible talks about the early history of the Christian church, up to about 70 AD. The following history is not in the Bible.
In 64 AD the Roman Emperor Nero blamed Christians for the Great Fire of Rome, and began to persecute them. Emperor Diocletian carried out the Great Persecution (303-311), in which Christians were arrested, tortured, mutilated and condemned to gladiatorial contests. The persecution ended in 311, when Galerius issued an edict which granted Christians the right to practice their religion.
In 312, the Emperor Constantine embraced Christianity, because he believed the Christian God helped him win a crucial battle for the imperial throne. Constantine became the patron of the Christian faith, supporting the church financially, building basilicas, granting privileges, promoting Christians to high offices, and endowed the church with land and other wealth. Eventually, Christianity became the state religion of the Roman Empire.
The church grew in two places, Rome and Constantinople. Rome fell to the Visigoths in 410, and began a period of turmoil. In 800, Charlemagne was crowned Holy Roman Emperor by the Pope, and re-established the dominance of the church in Europe.
In 1054, because of cultural, spiritual and political differences, the church was split into the Roman Catholic and Eastern Orthodox churches. The final break was over whether the Pope in Rome was supreme, or equal to the patriarchs of the Orthodox church.
According to the Catechism (official teachings), the Catholic Church is the ‘sole Church of Christ’, the Pope is the successor to the apostle Peter, and Catholic bishops have a lineal succession from the apostles.
Under Constantine, the church gained status and wealth, this led to more emphasis on ritual, and major corruption, which was the main cause of the Protestant Reformation.
Next: About Protestants