The transition from the late Roman world to that of medieval successor states is complex. As well as the establishment of Islam and Christianity as major religions, there were significant population shifts, including the barbarian settlements and the Viking expansions.
Monarchy and the Church were the two most important institutions, and they competed for political supremacy. Society was based on a feudal system, where the majority of peasants worked the land for their lord. However, the rapid growth of towns and an influential merchant class stimulated prosperity and challenged traditional social cultures.