Paul's early missionary work took place in the eastern Roman Empire. He traveled from Antioch in Syria to Cyprus and central Asia Minor (modern Turkey). Later venturing west to Greece, he established a Christian community in Philippi, whose residents included both Greeks and Romans. There Paul encountered hostility from those who viewed the Christian message as a threat to their tradition. At Thessalonica, Paul again met opposition from those who thought the gospel's claim that Jesus was the Messiah or king posed a threat to Roman rule. Non-Jews who accepted the gospel turned away from their traditional beliefs in Greco-Roman gods, which again seemed to make Christianity a threat to the social order.
Paul's earliest extant letter was written to the congregation at Thessalonica shortly after he had left the city. It shows Paul adapting the traditional format of an ancient letter to address the needs of the congregation in his absence. Paul probably dictated most of his letters to a scribe who did the actual writing. Whenever possible, a letter would be taken by a trusted friend to the intended recipients. When the letter arrived it was read aloud to the congregation. In time, Paul's letters would be copied and shared with other congregations, giving them an important role in shaping the beliefs and practices of the early church.
Traveling southward, Paul stopped in Athens and then settled in Corinth for a time. He lodged with Aquila and Priscilla, who were Jewish Christians. They worked together making tents. After forming a congregation in Corinth, Paul left the city and eventually relocated in Ephesus, which was another major urban center. There Paul received oral and written reports about the Corinthian congregation and responded with the letters known as 1 and 2 Corinthians.
The topics addressed by Paul's letter ranged widely. In letters to Corinth he addressed matters of factionalism, immorality, and spiritual gifts. When writing to Galatia, Paul reaffirmed that non-Jewish Christians do not need to become circumcised but are fully members of the Christian community by faith. In his letter to Philemon, he spoke about the need to accept a runaway slave as a brother in Christ. Toward the end of his ministry he wrote to the congregation at Rome, which he had not founded, summarizing his gospel for them before an anticipated visit.