A political system in which a vassal or retainer provided service to a lord in return for protection and land. Powerful nobles granted land to tenants whose land was called a fief. The tenant, or vassal, was obliged to follow his lord in war and perform other services including the administration of the lord’s affairs. In theory, either lord or vassal could end the relationship if the other party failed to perform his role. In Japan, the system was headed by the shogun rather than a king or emperor as in Europe.