How did a small band of Jesus’s followers, in a distant area of the Roman Empire, create the state religion? It didn’t happen quickly. In fact, it took almost 400 years, but Christianity slowly spread.
Early on, Rome’s reaction to the religion was mixed. Some emperors persecuted Christians, and others ignored them. The Roman official Pliny the Younger asked the Emperor Trajan, who ruled from 98 to 117 CE, how to treat Christians. [[The emperor replied in part, “They are not to be sought out; if they are denounced and proved to be guilty, they are to be punished, with this reservation, that whoever denies that he is a Christian and quite clearly proves it—that is, by worshipping our gods—he shall gain pardon.”*]] The religion grew in spite of persecution. It was always strong in the eastern part of the empire, where it had its roots. Large cities in the western empire also had churches. They started as small, secret groups that met in homes. The apostle Paul started a church in 50 CE in Rome, right under the emperor’s nose.
*From Pliny, “Letters,” in The Romans: From Village to Empire. M.T. Boatwright, D.J. Gargola, and R.J. Talbert, eds. Oxford University Press, 2004.