Church History in Plain Language

Era 3 · 312 – 590

The Christian Roman Empire

The persecuted church becomes the emperor's church, and must decide who Christ is, how to be holy in a Christian society, and what to do when Rome falls.

In 312 a Roman general marched on Rome under a Christian symbol and won. Within eighty years the faith that emperors had tried to stamp out became the empire's official religion. Shelley calls this the age of "the Christian Roman Empire." It is one of the most dramatic reversals in history.

Imperial favor brought enormous changes. There were grand basilicas, wealthy bishops, crowds of new converts and emperor-called councils. It also brought new dangers. The state now cared which theology won, and the losers could be exiled. Many Christians worried that the church was growing rich and lukewarm, and some fled to the desert to become monks.

This was also the great age of doctrine. Over a century and a half, a series of councils hammered out the church's teaching on two central questions. Is the Son truly God (Nicaea, 325)? How can Christ be both God and human (Chalcedon, 451)? The answers shaped Christianity forever. They also left lasting divisions, as churches in Egypt, Syria, Persia and Armenia refused some decisions.

In the West, meanwhile, the empire itself fell apart. Augustine of Hippo wrote The City of God to make sense of Rome's sack in 410. Bishops of Rome like Leo the Great stepped into the vacuum. The era closes in 590, when Gregory the Great became pope, standing on the threshold of the Middle Ages.

Timeline: The Christian Roman Empire (312 – 590)

350400450500550306 Constantine proclaimed emperor by his troops…318 Arius' teaching condemned in Alexandria320 Pachomius founds the first communal monaster…321 Sunday made a public day of rest328 Athanasius becomes bishop of Alexandria337 Constantine baptized on his deathbed354 Augustine born at Thagaste, North Africa359 Councils of Rimini and Seleucia favor Arian-…360 Basil writes his monastic rules in Cappadocia376 Goths cross the Danube into the empire381 First Council of Constantinople; Nicene Cree…381 Apollinarius' views condemned at Constantino…386 Conversion in a Milan garden391 Theodosius bans pagan sacrifice410 Alaric's Goths sack Rome410 Synod of Seleucia-Ctesiphon organizes the Pe…424 Persian church declares independence from We…430 John Cassian brings Egyptian monasticism to …430 Dies as Vandals besiege Hippo431 Council of Ephesus: Mary declared Theotokos;…440 Leo the Great becomes pope449 Leo's Tome sent to Constantinople476 Last Western emperor deposed by Odoacer489 Emperor Zeno closes the "School of the Persi…540 Rule of Saint Benedict written542 Jacob Baradaeus begins ordaining Miaphysite …553 Second Council of Constantinople tries to wi…568 Lombards invade Italy
Selected key dates from each chapter of this era. Click an event to read its chapter, or see every date in this era on the master timeline.

Chapters in this era

  1. 1ConstantineConstantine's conversion, the Edict of Milan, imperial favor, and how Christianity became Rome's official religion.
  2. 2Arius and the Council of NicaeaThe Arian controversy, the Council of Nicaea, Athanasius, the Cappadocians and the doctrine of the Trinity.
  3. 3Who Is Christ? Ephesus and ChalcedonApollinarius, Nestorius, Cyril, the "Mother of God," and the Council of Chalcedon's "two natures in one person."
  4. 4The Desert and the MonasteryAntony, Pachomius, the Desert Fathers and Mothers, Basil, Martin, Benedict, and the rise of Christian monasticism.
  5. 5Augustine of HippoAugustine's life and conversion, his battles with Manichees, Donatists and Pelagians, and The City of God.
  6. 6Rome Falls, the Papacy RisesBarbarian invasions, the end of the Western empire, Leo the Great, Clovis, and the papacy's growing role.
  7. 7Churches Beyond ChalcedonThe Oriental Orthodox churches and the Church of the East, and their remarkable spread across Asia.