As the Germanic kingdoms succeeded Roman authority in the West in the fifth century, Roman landlords were often simply replaced by Gothic or Germanic ones, with little change to the underlying situation. The process of rural self-sufficiency was given an abrupt boost in the eighth century, when normal trade in the Mediterranean Sea was disrupted. The thesis put forward by Henri Pirenne, disputed by many, supposes that the Arab conquests forced the medieval economy into even greater ruralisation and gave rise to the classic feudal pattern of varying degrees of servile peasantry underpinning a hierarchy of localised power centres.