In recent years, Sufism has become all but synonymous with the mystic poetry of Jalāl al-Dīn Rūmī (d. 1273) and the ritual "whirling" of dervishes from Turkey. This branch of Islam does, however, have a long, complex history, and spiritual retreat was only one aspect of its significance. In medieval Anatolia, Cities and Saints contends, Sufis made alliances that gave dervish lodges powers so vast that they were able to alter...