Feudalism was the system of "government" used during the Middle Ages. Feudalism was based on the amount of land owned by an individual. Feudalism was also based on the exchange of service for labor. Fuedalism was first concepted when Charles The Simple granted a viking leader a fief, then the viking leader pledged loyalty to Charles. A fief is a land grant that is usually given by a lord to his knights or vassals. The feudal system is based on mutual obligations. The lords granted vassals land so that vassals could permit knights to live on the manors and provide the whole manor with military protection. Lords benefitted from granting fiefs because they gained food from the serfs who lived there. Vassals permitted the serfs to live on their manors, so that serfs could produce food. In return for producing food the serfs recieved protection and a place to live. There was a very low standard of living during the time of feudalism. Serfs would bring their pigs into their house at night to keep their homes warm. They would also sleep on infested bales of hay.