Monarchy was the only viable form of government in the medieval era. Even when feudal lords dominated the political landscape of Europe, kings always remained lurking in the shadows of their more powerful vassals, waiting for opportunities to exercise their regal prerogatives.

One of the most interesting facets of medieval monarchy is that virtually all rulers devoted the majority of their reigns to expanding their realms, shoring up its defenses, or dealing with aggressive and defiant vassals. Charlemagne, arguably one of the greatest medieval rulers, if not the greatest, forged an empire by a policy of conquest and diplomacy. He maintained his empire by developing loyal groups of advisers and bureaucrats who made certain that the nobility would be held accountable to Charlemagne. William the Conqueror won his kingdom by conquest and maintained it by employing absolute and iron-fisted control. Louis VI typifies a...