In feudal Japan the hierarchical social system was dominated by powerful families who were given control of vast plots of land in return for rendering military service to the Emperor. This is strikingly similar to the kind of arrangements that existed for centuries in Europe.
The collapse of the Western half of the Roman Empire created a huge power vacuum which nobles were quite willing to fill. Although the king was technically the most powerful individual in each state, in actual fact the nobles were often much more powerful as they could demand concessions from the reigning monarch, safe in the knowledge that they could rely on private armies to defend their interests.
A similar situation existed in Imperial Japan. Here, although the Emperor was the most important political figure in the country, power was spread among wealthy landholding nobles. Each noble was lord of his domain, exercising complete control over every aspect of local life. As in Europe, Japanese nobles' peasants worked the land and were called upon to serve as soldiers. Civil wars regularly broke out in feudal Japan and, when they occurred, peasant soldiers were called into service.
Throughout the history of feudal Japan, ultimate power rested, not with the Emperor, but with powerful noble families (daimyo), warlords (shōgun) and their warriors (samurai). In feudal Europe weak monarchs were similarly often at the mercy of powerful nobles and their armed retainers.