The author provides an account of the cultural evolution of a new concept of leadership for both emperors and the church in the Christianising society based in the eastern Roman capital of Constantinople. The focus is the pivotal period from the establishment of Constantine the Great’s one-man rule through Byzantine rule over the eastern and western empires in the sixth and seventh centuries, ending with the rule of Irene as sole empress (797–802) and Charlemagne’s coronation in 800. Letters exemplify the late Roman transformation from a model of one-man (or one-family) rule to a more complex system of power sharing between religious authorities, which was under constant renegotiation, from the highest levels of governance under emperors and bishops to the lowest level of the parish led by local clergy. Increasing opportunities for women to exercise power, hand in hand with the episcopal leaders of the new church, also shaped imperial leadership ideals in new ways.

This chapter examines the urban development of Constantinople in Late Antiquity, tracing its transformation from a small Greek settlement into the capital of the Eastern Roman Empire. It focuses on three major phases of construction: Constantine’s foundation (324–37), the Theodosian expansion (379–450) and Justinian’s rebuilding efforts (527–65). The study explores key infrastructure projects, including city walls, forums, aqueducts, palaces, churches and harbours, demonstrating how these developments reshaped the city’s urban landscape. A central theme is the political and symbolic role of architecture in establishing Constantinople’s imperial identity. Constantine’s expansion laid the foundation for a monumental capital, incorporating existing Severan structures while introducing new landmarks such as the Forum of Constantine. The Theodosian period witnessed the construction of the formidable land walls and major religious buildings, further solidifying the city’s status as a Christian metropolis. Under Justinian, Constantinopolitan architecture reached its peak, with the reconstruction of Hagia Sophia serving as a defining moment in Byzantine building traditions. The chapter also addresses archaeological challenges, noting that while much of the ancient city has been lost due to war and modern urban development, ongoing excavations continue to provide valuable insights into Constantinople’s late antique transformation.

Constantine's role in calling the Council of Nicaea has long been recognized. But theological interests have overshadowed the political side of his decision-making. In the nineteenth century scholars coined the word “Caesaropapism” for imperial interference that they saw as a threat to the purity of the Church. But the ancient state operated on a different set of principles, and a political approach fills in important blanks in our understanding of the council. By the time Constantine took control of the eastern empire he had learned that the best way to deal with conflict in the Church was to assemble the largest number of bishops possible and have them settle the problem. This is the thinking behind his decision to ask all the bishops in the empire to settle the Arian question. This is why Nicaea became known as the first ecumenical (“world-wide”) council, though in reality almost all of the bishops present came from the East. Publicly, Constantine treated the bishops at Nicaea with respect and humility, but behind the scenes he worked to bring the opposing parties into agreement. The result was the Nicene Creed, still recited (in slightly different form) by Christians today.