'Abd al-Mu'min (c.1094–1163) did not establish the first caliphate in the Islamic West, but his encompassed more territory than any that had preceded it. As leader of the Almohads, a politico-religious movement grounded in an uncompromising belief in the unity of God, he unified for the first time the whole of North Africa west of Egypt, and conquered much of southern Spain.

Studying every facet of 'Abd al-Mu'min's rule, from his violent repression of opposition to the flourishing of scholarship during his reign, Maribel Fierro reveals an intelligent leader and a skilled military commander who sought to build a lasting caliphate across disparate and diverse societies.