Christianization of the Roman Empire

The gradual spread of Christian belief and institutions across the Roman Empire, especially after imperial toleration began in the fourth century. It transformed religious practice, political authority, and public life without happening uniformly or at once.

Edict of Milan: A 313 agreement associated with Constantine and Licinius that granted religious toleration to Christians in the Roman Empire. It ended official persecution and allowed Christian communities to operate openly.
Early Christianity: The Christian movement and its communities from the first century through the early fourth century. Its existing networks and beliefs formed the foundation for later imperial expansion.
Theodosius I: Roman emperor from 379 to 395 who made Nicene Christianity the empire’s official religious standard. His reign consolidated the legal status of Nicene Christianity.
Christianity and Roman law: The interaction between Christian norms and Roman legislation, especially in the later empire. Imperial laws increasingly reflected Christian priorities and regulated religious practice.
Council of Nicaea: A 325 council convened by Constantine that addressed disputes over Christ’s relationship to God the Father. Imperial sponsorship of this council linked doctrinal unity to political stability.
Diocletianic Persecution: The empire-wide persecution of Christians begun under Diocletian in 303. Its failure to eliminate Christianity preceded the dramatic policy reversal under Constantine.
Ambrose of Milan: Bishop of Milan from 374 to 397, known for his influence over imperial religious policy. His confrontation with Theodosius demonstrated a bishop’s capacity to challenge an emperor.
Religious persecution in the Roman Empire: State coercion against religious groups in the Roman Empire, including both anti-Christian and anti-pagan measures. The shift from persecuted minority to favored religion also brought coercion against rivals.
Constantinian shift: The change in Christianity’s status after Constantine’s conversion and imperial patronage in the early fourth century. It marks the turn from a persecuted religion toward one supported by emperors.
Battle of the Milvian Bridge: The 312 battle in which Constantine defeated Maxentius near Rome and secured control of the western empire. Constantine’s victory preceded his public support for Christianity.

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