This insightful history sheds light on the early Christian church of Assyria, during the time of the Sassanid Persian Empire that ruled from the 2nd to the 7th centuries AD. The author's mission is to provide a coherent and sequential narrative of the development of Christianity during the period, that readers may understand how the Christian beliefs took root and flourished. Later, the established church of the east was threatened by persecutions from figures who opposed the spread of Christianity. The sophisticated nature of the church hierarchy, and the extent of its influence upon the rulers and political elements of the Sassanid Persian state, are detailed. Prosperous and ascendant, Sassanid Persia proved to be fertile ground for the development of the new religious culture. An atmosphere of tolerance saw a variety of religions practiced in the Middle East, with Christianity in the ascendance. Despite this, many areas in the Sassanid Empire had little or no Christian worship, and churches were never built upon anywhere close to all the Empire's territory. This period of expansion proved short-lived: by the 4th century persecutions had grown in frequency, and in the 7th century a calamitous war between Persia and Byzantine was accompanied by the spread of a new creed - Islam. Fortuitously the Assyrian church negotiated status as a minority religion, which afforded it legal protection and continuation for centuries to follow.