By giving equal time to the Middle Periods, Hodgson was able to reassess the impact of the Mongol invasions on West Asia. As he shows, it was catastrophic, leading to the depopulation of much of the countryside, the destruction of many cities and the collapse of the political and cultural infrastructure. Moreover, the Mongols did not depart, as barbarian hordes generally did. They remained in place, and Mongol successor states ruled western Asia until the rubble were profoundly marked by the experience, their possibilities of action sharply constrained by the intensely adverse impact of two centuries of pastoralist depredations. While Islam was enduring two centuries of decline and cultural turmoil under the Mongol yoke, western Europe was undergoing the series of transformations that were to give rise to modernity. It we would understand the rise of the West, Hodgson cautions us, we must first grasp the meaning of parallel history.