Christians had always been subject to local discrimination in the empire, but early emperors were reluctant to issue general laws against the sect. It was not until the 250s, under the reigns of Decius and Valerian, that such laws were passed. Under this legislation, Christians were compelled to sacrifice to Roman gods or face imprisonment and execution.
After Gallienus‘s accession in 260, these laws went into abeyance. Diocletian‘s assumption of power in 284 did not mark an immediate reversal of imperial inattention to Christianity, but it did herald a gradual shift in official attitudes toward religious minorities. In the first fifteen years of his rule, Diocletian purged the army of Christians, condemned Manicheans to death, and surrounded himself with public opponents of Christianity. Diocletian’s preference for activist government, combined with his self-image as a restorer of past Roman glory, foreboded the most pervasive persecution in Roman history. In the winter of 302, Galerius urged Diocletian to begin a general persecution of the Christians. Diocletian was wary, and asked the oracle of Apollo for guidance. The oracle’s reply was read as an endorsement of Galerius’s position, and a general persecution was called on February 24, 303.
Before the end of February 303, a fire destroyed part of the imperial palace of Nicomedia. Galerius convinced Diocletian that the culprits were Christian conspirators who had plotted with palace eunuchs. An investigation into the act was commissioned, but no responsible party was found. Executions followed. The palace eunuchs Dorotheus and Gorgonius were eliminated. One individual, a Peter, was stripped, raised high, and scourged. Salt and vinegar were poured in his wounds, and he was slowly boiled over an open flame. The executions continued until at least April 24, 303, when six individuals, including the bishop Anthimus, were decapitated. The persecution intensified. Now presbyters and other clergymen could be arrested without having even been accused of a crime, and condemned to death. A second fire appeared sixteen days after the first. Galerius left the city, declaring it unsafe. Diocletian would soon follow. Lactantius blamed Galerius’s allies for setting the fire; Constantine, in a later reminiscence, would attribute the fire to “lightning from heaven”.
Lactantius, still living in Nicomedia, saw the beginnings of the apocalypse in Diocletian’s persecution. Lactantius’s writings during the persecution exhibit both bitterness and Christian triumphalism. His eschatology runs directly counter to Tetrarchic claims to “renewal”. Diocletian asserted that he had instituted a new era of security and peace; Lactantius saw the beginning of a cosmic revolution.
Persecutory policies varied in intensity across the empire. Where Galerius and Diocletian were avid persecutors, Constantius was unenthusiastic. Later persecutory edicts, including the calls for universal sacrifice, were not applied in his domain. His son, Constantine, on taking the imperial office in 306, restored Christians to full legal equality and returned property that had been confiscated during the persecution. In Italy in 306, the usurper Maxentius ousted Maximian‘s successor Severus, promising full religious toleration. Galerius ended the persecution in the East in 311, but it was resumed in Egypt, Palestine, and Asia Minor by his successor, Maximinus. Constantine and Licinius, Severus’s successor, signed the Edict of Milan in 313, which offered a more comprehensive acceptance of Christianity than Galerius’s edict had provided. Licinius ousted Maximinus in 313, bringing an end to persecution in the East.