Hereditary Alliances Hereditary alliances are alliances formed by at least two princes and including their heirs, descendants and successors. The signatories promised each other friendship, advice, protection, and help against all others, normally excluding the pope, the emperor, and sometimes other named princes. The distinguishing characteristic of such alliances is their perpetual validity. Their duration without limit was to be guaranteed by the involvement of all future generations of heirs. The aim was to bring about a lasting peace between the signatories, their lands, and their subjects. From their late medieval origins as alliances devoted to eternal friendship and mutual defence, they developed in the fifteenth and sixteenth century into neighbourhood or regional treaties, which were designed to foster peaceful relations between princes and territories under the rule of law. To this end, they contained complex rules for the arbitration of disputes and for cross-border legal assistance.