At Milan, Constantine and Licinius reached an agreement establishing broad religious toleration and restoring confiscated Christian property—an important step in ending official persecution and normalizing Christianity in imperial public life.
Constantine convened a major Western synod at Arles to address the Donatist schism, an early example of imperial authority being used to manage intra-Christian disputes and promote ecclesiastical unity.
Constantine defeated Licinius at Cibalae during their growing conflict, a turning point in the breakdown of their power-sharing and a step on Constantine’s path toward sole rule.
Constantine consecrated the site of his new capital at Byzantium, beginning the transformation of the city into an imperial residence and a lasting center of Christian imperial power in the eastern Mediterranean.
Constantine convened the Council of Nicaea to address the Arian controversy and other church matters; its creed and decisions became foundational for defining orthodox doctrine and for imperial involvement in church unity.
Constantine ordered the execution of his eldest son Crispus and soon after that of Empress Fausta. Ancient sources differ on motives, but the episode reshaped the dynastic picture as the new capital project advanced.
Constantine presided over the formal dedication of his rebuilt city—known as Constantinople (New Rome)—cementing a new political and ecclesiastical center that would dominate late antique and medieval eastern Roman history.
Summoned under Constantine, the Council of Tyre (335) heard charges against Athanasius of Alexandria and led to his deposition and exile, illustrating how doctrinal and episcopal conflicts remained entangled with imperial power after Nicaea.
Constantine I: Constantineople and the Christianization of the Empire (306–337 CE)
