This significant new work focuses on the formation and fragmentation of an Arab-Muslim state and its society in Sicily and south Italy between 800 and 1300, which led to the formation of an enduring Muslim--Christian frontier during the age of the Crusades. It examines the long- and short-term impact of Muslim authority in regions that were to fall into the hands of European rulers, and explains how and why Muslim and Norman conquests imported radically different dynamics to the central Mediterranean. On the island of Sicily, a majority Muslim population came to be ruled by Christian kings who adopted and adapted political ideologies from Mediterranean regimes, while absorbing cultural influences from the diverse peoples over whom they reigned. This work provides an engaging, expert and wide-ranging introduction to the subject, and offers fresh, clear insights into the evolution of both Europe and the Islamic world.