MUMBAI: As two billion Christians prepare to celebrate the Christmas season, news broadcaster CNN offers a broad-ranging documentary on the tumultuous early years of Christianity - from the crucifixion of Jesus Christ to the conversion of Constantine, the Roman emperor who first legalised Christianity in 313 A.D.

The special CNN Presents: After Jesus - The First Christians airs on 22 December at 8:30 pm, 26 December at 8:30 am, 30 December at 7:30 pm. It examines how the earliest Christians spread their message, despite internal strife over the faith and violent persecution by Rome.

Immediately following Jesus' crucifixion and resurrection, the first Christians were challenged to define their faith. Two of Jesus' disciples - Peter, who preached that the followers of Jesus had to be Jewish, and Paul who argued that this new faith must be available to all - would emerge as Christianity's first and most influential leaders.

Their eventual consensus, that Christianity would be available to all through conversion, and their missionary zeal throughout the Roman Empire, helped the new faith to spread rapidly. But Christianity's growing power was also a threat to the empire, so the Romans killed Peter and Paul and other early leaders.

Christians were so brutally persecuted that Christianity's survival was repeatedly in danger. That Christianity eventually became the world's largest religion is perhaps the faith's second biggest miracle.

CNN examined archaeological evidence and spoke with the most renowned authorities on the ancient church to answer "the" question at the heart of the story: How did Jesus, a wandering rabbi from the hinterland, and his illiterate followers, triumph over Roman persecution and establish a worldwide faith?

Viewers may be surprised to learn that followers of some early branches of Christianity believed in morethan one god; that there were many more Gospels than those included in the New Testament; and that Christmas was originally a springtime celebration.

There was also a group of Christians - the Gnostics -who believed that man's existence on Earth was a mistake and that salvation required a mystical experience of self-discovery and self-realisation. They wrote their own Gospels, and their power struggle with the orthodox Christians was a threat to the new faith.

The special also examines the Biblical history of Israel, the destruction of the Temple of Jerusalem and the events during the Council of Nicaea that have come to define modern Christian orthodoxy.