Expectation of a redeemer is a widespread phenomenon across many civilizations. Classical Islamic traditions maintain that the mahdi will transform our world by making Islam the sole religion, and that he will do so in collaboration with Jesus, who will return as a Muslim and play a major role in this apocalyptic endeavour.

While the messianic idea has been most often discussed in relation to Shi'i Islam, it is highly important in the Sunni branch as well. In this groundbreaking work, Yohanan Friedmann explores its roots in Sunni Islam, and studies four major mahdi claimants - Ibn Tumart, Sayyid Muhammad Jawnpuri, Muhammad Ahmad and Mirza Ghulam Ahmad - who made a considerable impact in the regions where they emerged. Focusing on their religious thought, and relating it to classical Muslim ideas on the apocalypse, he examines their movements and considers their achievements, failures and legacies - including the ways in which they prefigured some radical Islamic groups of modern times.