A scholarly and authoritative history of the emergence and growth of Islam in Iran during the early and later medieval periods. This book, by I. P. Petrushevsky, the foremost Soviet Iranologist, was originally published in Russia in 1966. After discussing the Arabian environment in which the faith of Islam arose, and the character--legal, social and doctrinal--of the new message, the author moves on to trace the peculiarly Iranian development of Islamic beliefs, the schisms which arose in its early history, and the eventual creation of a Sunni orthodoxy. Written from the Russian perspective, with Russia's long contact with Iranian and Turkish Muslim neighbors, it provides a stimulating and salutary balance to the study of the Islamic world.