This is the third volume in a series on the history of warfare. It begins in the time of Charlemagne, who maintained a military system of freemen and vassals bound to him in service for lands granted in fief. The text attempts to recreate famous events such as the Battle of Hastings and movements like the Crusades. The author describes how feudal military organization varied in different countries and why the knightly forces could not hold up against the Normans. He studies military developments in the kingdoms that rose with the collapse of the Carolingian Empire, as well as the trend toward mercenary armies.