From the Council of Chalcedon up to Justinian’s reconquest of Italy (451-536), numerous imperial interventions in church affairs reflect the complexity of the conflict which opposed the major ecclesiastical sees, Rome, Constantinople and Alexandria. In addition to changes in doctrine, this period of history saw major changes in the organization and power structure of the Church. Each see tried to define principles of government based on its particular understanding of the tradition and of the canons, to strengthen its influence, and to justify its claims of authority. To this end, imperial and public support had to be secured. This involved, among other things, the development of symbolic discourse and complex editorial campaigns. From this remarkable conflict emerged a tremendously consequential concept: Justinian’s pentarchic model.