A rough balance of political power between monarchs and a militarized landed aristocracy characterized medieval Western Europe. Scholars have argued that this balance of power contributed to a tradition of limited government and constitutional bargaining. I argue that 5th- and 6th-century barbarian settlements created a foundation for this balance of power. The settlements provided barbarians with allotments of lands or taxes due from the lands. The allotments served to align the incentives of barbarian warriors and Roman landowners, and realign the incentives of barbarian warriors and their leadership elite. Barbarian military forces became decentralized and the warriors became political powerful shareholders of the realm.