Medieval Europe was a complex political and social system. Within this system, security was provided by local rulers and their knights, who lived in fortified towns and strong castles. Freedom was given by feudal rulers to their followers and clients to the degree that they determined, while keeping the general order was the responsibility of the emperor, albeit in a limited way. Justice was ensured by political and religious rulers alike, but also in an unequal way, being far more skewed in favor of the upper classes.