Feudalism arose out of the decline of the Western Roman Empire across Europe, when the rise of invasions by barbarian tribes led landowners to seek protection from soldiers. Under the feudal system, kings granted land called fiefs to nobles who pledged their loyalty in exchange. The system was supported by the agricultural labor of serfs who worked the land for the landowners. The feudal system provided a social and political order to Western Europe after the fall of Rome. In the 8th century CE, French King Charlemagne unified a large portion of Western Europe under the Holy Roman Empire. Through violence, Charlemagne established stability and built a Christian empire. After his death, however, his descendants could not maintain the same level of control, and the empire was divided once more into smaller feudal kingdoms due to political upheaval.