A contemporary historian who served the Mamluk Sultanate, Ibn Khaldun astutely recognized the applicability of his Cyclical Theory of History to the evolution of Islamic history during the period covered in this chapter. By the eighth century, Islam became the predominant social and political unifier of the Middle East. And for the next nine hundred years, various caliphates used family and religion as tools to rule the region. However, these caliphates faced religiously-inspired revolts that challenged their authority. Quelling these revolts weakened the regimes, often leading to greater decentralization and the fragmentation of empires. Into these vacuums of power, new families armed with tribal ‘asabiyah and a novel religious ideology came forth to supplant a once dominant group who had succumbed to the wiles of civilization and whose influence gradually waned in the face of insurgent desert peoples.