By far the largest segment of European society was the serfs or peasants. Serfs were excluded from the feudal system, and for good reason. When a man became the vassal of a feudal lord, as his contribution to the contract he almost always brought with him arms, armor, and a company of armed fighters. Serfs lacked the weapons, training, and pedigree necessary to join the warrior elite. They were rural workers who, in exchange for protection and sustenance, were prepared to work the land for Europe's ruling feudal class.

Serfs lived on self-sustaining economic units called manors, which were part of the lord's domain. By law, serfs were the property of the lord. In fact, it was not uncommon for a serf to be sold like a slave. The land they tilled and the home in which they resided belonged to the lord of the...