Final answer:
The feudal system developed in medieval Europe primarily due to the need for security. Lords granted lands to fighters as fiefs in exchange for their service, creating a system of unequal relationships. This provided protection and stability in a time of constant raiders and threats of violence.
Step-by-step explanation:
One of the primary reasons that the feudal system developed in medieval Europe was the need for security. After the fall of the Carolingian empire, lords sought to protect their territories and peasants by granting lands to fighters as fiefs. In exchange for these lands, the fighters became vassals of the lords and pledged their service, primarily military, to the lord. This system of unequal relationships provided security and stability in a time of constant raiders and threats of violence.