After the fall of Charlemagne's empire, feudalism emerged as the dominant political system in Western Europe. Feudalism was based on the reciprocal relationship between lords and vassals, where lords would grant land to vassals in exchange for loyalty and military service. By the mid-1000s, most of Western Europe was organized around feudal relationships, with kings acting as supreme lords and lesser nobles serving as vassals and granting parts of their fiefs to their own knights. This system helped smaller territories maintain control and protection more effectively than a large empire in the unstable context of Viking invasions and internal conflicts.