This is a history of the people, struggles, defeats and victories, ideas and actions that together comprise the history of the first 1000 years of Christianity. It ranges across much of Asia, North Africa and Europe. It both captures the immediacy of decisive moments and explains how by the end of the period Christianity had become the dominant factor in political power and cultural life throughout the region. By establishing itself within the framework of two empires, the Roman and the Persian Sasanian, Christendom inherited from its beginnings their double universalism. The author traces the history of the distinctly Eastern Christendoms, centred first in Byzantium and later spreading to the Balkans and to Russia, and of Western Christendom focused on Rome but with powerfully independent centres in France, Germany, England and Ireland. He recreates the vibrancy of Christian cultures and their claims to be the universal "true" Christianity, and shows how the rise of centralized forms of Christianity were associated with the renewed imperial systems of Byzantium and the Carolingian Empire. Peter Brown examines the impact of other religious traditions on the development of Christianity. He describes reactions to the explosive rise of Islam, and explains how, especially in North and Eastern Europe, the memories of a pagan past became part of the culture of what was now an officially Christian world. By AD 1000, a distinctive relation between past and present, between profane and sacred, had emerged in Western Christendom, and a civilization that was by then irrevocably different from the Christendoms of the East.