"In the following pages I have tried to explain, as simply and concisely as possible, the historical significance of the feudal system. . . . My purpose has not been to give a comprehensive description of Europe in the feudal age, or even of feudal society. I have taken for granted that the reader will be familiar with the main political events of the Middle ages: the barbarian invasions, the formation of the Carolingian Empire, the establishment of the later monarchies, the Crusades, and the like. I have omitted all but cursory mention of the manorial system and the revival of commerce . . ....