What did the feudal system protect medieval European society from?

The feudal system protected medieval European society from external threats, such as invasions by Vikings, Magyars, and Saracens, by providing a structured hierarchy of loyalty and military service. Lords offered protection in exchange for land and service from vassals, creating a network of mutual obligations that helped maintain local security. Additionally, it fostered stability and order in a time of political fragmentation, as power was decentralized and communities relied on local governance and defense.