The ‘Abbasid Caliphate in Baghdad, beginning in 749 A.D., ushered in the Golden Age of Islamic civilization in its eastern regions and exerted considerable influence from the Mediterranean basin to the Far East until the Mongol destruction of its capital in 1258. This book analyzes the role of Muslim messianic and apocalyptic beliefs in the development of the 'Abbasid Caliphate to highlight connections between charismatic authority and institutional developments in the early ninth century. The author challenges traditional sociological views that marginalize messianic beliefs as oppositional ideologies of disfranchised social classes to be used against the political establishment. His discourse brings the subject to a new level of analysis and understanding, showing not only the strong influence of the new religion of Islam’s messianic and apocalyptic propensities — based in part on the Qur’an’s message about judgment and the end of the world—but also detailing how the neighboring older religions of Zoroastrianism, Judaism, and Christianity held parallel beliefs along similar lines, although obviously with differing aims and outcomes. Of particular interest, according to the editor, is the author’s refreshing consideration and coherent explication of messianic beliefs and apocalyptic expectations as spiritually powerful motivators for political, social, and personal action and not simply realpolitik.