The foundation of the Sasanian Empire in Persia in AD 224 established a formidable new power on the Roman Empire's eastern frontier, and relations over the next four centuries proved turbulent. This book provides a chronological narrative of their relationship, supported by a substantial collection of translated sources illustrating structural patterns. The political goals of the two sides, their military confrontations and their diplomatic solutions are discussed, as well as the common interests between the two powers. Special attention is given to the situation of Arabia and Armenia, to economic aspects, the protection of the frontiers, the religious life in both empires and the channels of communication between East and West. Considerable attention is also paid to exploring the role played by the Sasanians in the history of the ancient Near East. The book will prove invaluable for students and non-specialists interested in late antiquity and early Byzantium.