Obedience was no longer neccesarily included in the oath formula. "By this oath I promise to be faithful to my lord, the very pious Emperor Charles, as according to custom and right a vasall owns faith towards his lord, to guard his realm and protect his rights. And I will keep this my sworn oath henceforth as is in my power, and may God, Creator of heaven and earth, and these holy relics help me." (1) Often the oath of fealty is defined in a 'negative' way: not to do anything that may give harm or disadvantage to the lord, "...to ensure the king by an oath of fidelity not to do anything against his life and his body, and not to take him prisoner to his disadvantage..." (2) The lord, too, had duties towards his vasalls, besides fidelity from his side it was mostly protection in form of military aid in case the vasall was attacked, and maintenance, fe. by giving him a beneficium. In addition to the afore mentioned fidelty, the vasall owed his lord consilium et auxilium, ie. he had to visit his lord on days of council and judgement and function as an advisor. Auxilium meant military aid as a mounted knight, together with his retainers, if he had; but it also could involve payment of ransom, or giving financial support in case of great celebrations such as marriage. High standing vasalls of a king could be asked to bring 500 or 1000 warriors to a war, part of them fully equipped kinghts. Therefore, vassalty was mostly a military institution.
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