Christianity at first appeared to the Roman authorities as a form of Judaism, which was tolerated, but Jewish agitation against the Christians revealed its separate identity. The secrecy of the early Christian rites and misunderstanding of Christian language (e.g. Jn. 6: 35) and of the agape and Eucharist led pagans to suppose them guilty of flagitia, promiscuity, incest, and cannibalism. This fact explains why Nero in 64 could make them scapegoats for the fire in Rome. From then on persecution continued intermittently. It is attested under Domitian, and Pliny (q.v.) assumed that avowed Christians as such deserved death. The Emp. Trajan and his successors were unwilling to withstand public indignation against the Christians, who were alienated from ordinary social life. Persecutions, though attested in every reign of any length, were until 249 not initiated by the central government and were sporadic and ineffectual.
As the Church grew in strength and respectability, popular hostility abated, but in the mid-3rd cent. some Emperors took more seriously the conception that Rome's welfare rested on the favour of the gods. In 249 Decius commanded all subjects to sacrifice and obtain certificates of their obedience. Those who refused were marked out as Christians and suffered accordingly. The persecution did not outlast Decius' death in 251. Valerian in 257 forbade Christian meetings and ordered the clergy to sacrifice; in 258 he subjected them to death and high-ranking laity to other severe penalties. He was captured by the Persians in 260 and Christians resumed their meetings and received back their property. Systematic persecution was resumed in the later years of Diocletian (q.v.). In 299 he took steps to rid the army and court of Christians, but only in 303 did he issue edicts of general persecution. These increased in severity until sacrifice was enjoined on all subjects. A fearful persecution ensued throughout the Empire, though its intensity varied in different areas. After the abdication of Diocletian and his co-Augustus in 305, it subsided in the W., but continued in the E. until Galerius issued an edict of toleration in 311. Constantine, on acceding to power in Gaul and Britain in 306 had granted the Christians toleration and restitution of their possessions and Maxentius had followed suit in Italy in 311; in the so-called Edict of Milan (313) Licinius made the same concessions in the E.
The victims of persecution might be executed; they enjoyed the fame of martyrs. Many Christians were imprisoned for a time, or sent to the mines; survivors, who had often endured torture used to induce apostasy, acquired prestige as confessors. Many, too, recanted, or persuaded the authorities they had done so. Controversy about whether, and on what conditions, these lapsi, libellatici, or traditores might be reconciled, gave rise to the Novatian, Melitian, and Donatist schisms.