
The largest fiefs are those given directly by monarchs to noblemen or barons, who then subcontract parts of these fiefs to vassals of their own. The vassal does homage to the lord, formalizing the relationship. The lord gives the vassal an income-yielding fief ( fehu-od in Frankish, the basis of the word 'feudal'). Thus there develops the relationship between lord and vassal which is at the heart of feudalism. This act of generosity, ultimately for his own benefit, requires an oath of loyalty in return. Charles Martel grants his nobles rights over tracts of land, to yield the income with which they can provide fighting men for his army. The feudal system comes into focus during the 8th century, when the Carolingian dynasty is expanding its territory. Transcending that, and dependent upon it, is the interconnecting network of loyalties and obligations which make up feudalism.

The central economic feature is the manorial system. In medieval Europe the system is more complex.
WESTERN EUROPE FEUDAL KINGDOMS WORLD MAP FREE
In ancient Sparta, where all free men are warriors, the support comes from the defeated and enslaved peasants of Messenia, known as the helots. In a simple economy this means that the produce of an appropriate number of peasants or serfs must underwrite the expenses of the fighting man.

At the heart of feudalism is a basic idea common to any society with a warrior caste.
