The feudal system was perhaps the strongest venue for the exercise of monarchic power in history. Not only were the citizens physically protected by the walls of the castles of the monarch, but their actual livelihood was in his hands. (Her hands in some European monarchies.) In return for this protection, the peasantry gave tithes and military service to the monarch, who stayed in power by winning wars and resisting invaders. The succession of monarchs was based on “divine right” passed down by heredity, and when the obvious successor was challenged by another (legitimate son vs. illegitimate son, for example), the outcome was often determined by the “kingliness” of the behavior of the two challengers, so that the status was sometimes assessed by the populus. There was no higher authority than the monarch, although until the establishment of the Church of England the Catholic hierarchy in Rome sought to gain de facto veto power by threatening excommunication, even war, to any monarch who sought to contradict its will (by, for example, divorce). Some challenges to monarchic status resulted in the Magna Carta (q.v.).