How did the gospel spread through the whole Roman Empire in Paul's lifetime without modern media?
The gospel spread through Roman soldiers who guarded Paul during his house arrest in Rome. As those soldiers rotated to posts across the empire, they carried the message they had heard from Paul. Through this network, the then-known world heard the plan of salvation within Paul's thirty-year ministry.
Les explains that people wonder how the gospel covered the then-known world, primarily the Roman Empire, without radio, television, or the printed page. Paul’s ministry lasted about thirty years—he was converted around 37 and put to death in 67. While under house arrest in Rome, Roman soldiers guarded him 24 hours a day. The Roman army rotated soldiers in places of duty, so during those two or three years many unknown soldiers spent time in Paul’s house. As they rotated out to the far reaches of the empire, they went as believers; some even reached Caesar’s palace. Paul ministered to his guards, and they in turn carried the plan of salvation throughout the empire.