This volume examines developments in the churches of the East and the West in the High Middle Ages, including major Western movements such as the reform papacy, the crusades, and scholasticism, and their impact on the Eastern Church. Concurrently, the author explores the theological and spiritual tides that spread from Byzantium to the northern regions of the Balkans and Rus', and lastly recounts the stories of the native churches of Egypt, Ethiopia, Syria, Armenia, and Georgia. THE CHURCH IN HISTORY SERIES of St Vladimir's Seminary Press balances the approaches of the abundance of church histories written from a Western Christian point of view. Series authors-in the unique position of being Orthodox scholars conversant with Western scholarship-have taken on the task of analyzing complicated primary sources and thoroughly critiquing modern scholarly literature to guide readers through the maze of centuries of church formation and life.