After the fall of Rome, Europe fell into a period of economic stagnation and political disunity. Power shifted from a centralized state to local rulers within a feudal system. Most of Europe remained decentralized throughout the post-classical era, which stalled innovation and economic production in the region. However, there were strong states such as the Byzantines, Vikings, and Kievan Rus that remained an outlier to the norm in medieval Europe. These states continued to participate in global trade and preserved the culture of the classical era.