The Spread of Christianity
It would be impossible to talk about the growth of Christianity without mentioning the apostle Paul, who was not one of the original apostles. In fact, Paul was an outspoken opponent of Jesus' teachings at first, both during Jesus' life and after his death. It is then a surprise that Paul became a vigilant missionary after he was strangely blinded on the road to Damascus. According to the Bible, the Holy Spirit visited Paul and returned his sight, which then led Paul, as a new convert, to spread the message of Jesus and establish Christianity throughout the world—at least the parts he could reach in a lifetime.
Paul became the perfect ambassador for Christianity and was able to bridge the gap among Jews, Romans, and Greeks. He had been raised strictly in Judaism; he spoke fluent Greek; and he was a Roman citizen. He was also educated in Greek literature and thought and could, therefore, express the doctrines and teachings of Jesus to the Gentiles. As a Roman citizen, he had certain freedoms that allowed him to travel and continue the work that Jesus began. Paul managed to bring his message to areas of the world that Jesus never reached, such as Turkey (then known as Asia Minor) and Greece.
According to the scriptures, in particular the Book of Acts in the New Testament, Paul made three major trips during his life:
Palestine and Antioch (Syria)
Thessalonica (ancient Macedonia)
Philippi and then on to Corinth and Turkey (Asia Minor)
However, it wasn't long before authorities caught on to Paul and his continuing Christian teaching. Upon his return to Jerusalem, after he opened a church in Ephesus (a city in the country we now call Turkey), Jewish authorities arrested Paul, fearing an uprising of Jesus' followers and the possible undermining of Judaism. Paul appealed his case to Rome, where he spent the rest of his life awaiting trial. In A.D. 64, Emperor Nero decided to eradicate the Christians from Rome, and Paul was never seen or heard from again.
New Christian Ground
After the fall of Jerusalem to the Romans (about A.D. 70), the seat of the Christian faith was forced to find new ground. By that time, Christianity had gathered thousands of followers and was powerful enough that finding a new home did not take very long. The second home of the Christian faith became, not surprisingly, Antioch in Syria, where Paul had spent a good amount of time preaching. It seemed the most likely place for the new church home, but it didn't stop there.
On his travels, Paul managed to convert many Gentiles to the teachings of Jesus Christ and during his third trip, he wrote his famous letter to the Thessalonians, which later became a book in the New Testament.
Paul Leaves His Mark
Christianity found its way to India and northern Africa, as Paul made his way to Italy and Spain. By the end of the fourth century—400 years after the birth of Jesus, there were about 500,000 people living in Antioch and half the population was Christian. By the middle of the third century, there were 30,000 Christians living in Rome.
However, Christianity did not spread as quickly to the West as it did to the East. France (or Gaul as it was known then) only had one known church, based in Lyon, by the middle of the first century, and there were only a few churches in Spain, despite Paul's work.