Just as the breakdown of centralized monarchical government gave rise to feudalism, the reverse was true: The erosion and ultimate collapse of the feudal system during the final centuries of the Middle Ages was caused in large measure by the rise of national monarchies. Essentially, feudalism harbored and even nurtured the seeds of its own ruin. Within the feudal hierarchy, the king was acknowledged as superior in standing to all other feudal lords. More importantly, by feudal custom, all land theoretically belonged to the king. As a result, the nobles controlling specified areas of land had to acknowledge receipt of that land from the king, thereby becoming his vassals. As the king's vassals, custom obligated those noblemen to swear homage to him and promise to fulfill specified feudal obligations. Therein lay the rub, since any member of the noble class who ignored his feudal...