Pax Romana simply means “Peace of Rome” and refers to the tranquility and security that the Roman Empire brought to the Mediterranean world. The Pax Romana lasted from the reign of Caesar Augustus (27 BC–AD 14) to that of Caesar Marcus Aurelius (AD 161–180). At the time of Christ and during the first generation of the church, much of the world was unified under Roman authority and enjoyed a relative peace.
God could have chosen to spread the gospel by writing it in the sky or sending angels to every corner of the world. However, He chose ordinary people (albeit empowered by His Spirit) to spread the gospel. Occasionally, there were miraculous interventions (like Philip being whisked away to another place after sharing the gospel with the Ethiopian in the desert—Acts 8:39–40), but most of the time, those early Christians had to travel from place to place by the normally available means—walking, on a cart pulled by an animal, on an animal, or on a boat. Sometimes the Word was spread by means of written letters, and these letters had to be carried by hand over many miles.
The Pax Romana provided an environment that allowed safe travel throughout the Roman Empire. A road system connecting towns facilitated easier travel. Roman discipline cut down on crime on the roads and piracy on the Mediterranean Sea, making travel safer. Warfare, which was the plague of the ancient world, was at a minimum within the borders of the empire. Therefore, missionaries and travelers could travel with relative ease, increasing mobility and the spread of the gospel. Likewise, business was booming, so Christians often traveled from city to city, spreading the gospel in the course of their normal commercial activities.
The Pax Romana also had an impact on language, as Greek became the common language used throughout the Roman Empire. In the early church, there were times when God enabled people to speak in languages they had not learned in order to communicate the gospel to people in their native languages (Acts 2:7–11). However, most of the time, people used Greek, and the gospel spread from person to person in that language. Because of the commonality of language provided by the Pax Romana, the New Testament, written in Koine Greek, was easily accessible to people in every part of the empire. People from disparate parts of the empire could still communicate with each other, and Paul’s epistles could make their rounds to the churches and be understood by all.
Finally, Rome was generally tolerant when it came to religious matters. As long as the Christians were not suspected of “disturbing the peace,” i.e., the peace of Rome, they were allowed to worship and evangelize. (Notice several times in the book of Acts, the Romans really start to take notice when Paul is accused of disturbing the peace—Acts 16:20–21; 19:31–32; 24:2–5, 12.)
In summary, the Pax Romana provided ease of travel due to a well-developed and maintained road system, safety in travel due to the absence of warfare and stepped-up crime prevention, and the extensive use of Greek as the common language. These developments provided the perfect environment for the gospel to spread quickly throughout the “civilized world.” Civil protections for citizens and residents of the empire, as long as they were not considered a threat to the Pax Romana, also allowed the early Christians some freedom in sharing an unpopular message.