In Europe during the Middle Ages, ransom became an important custom of chivalric warfare. An important knight, especially nobility or royalty, was worth a significant sum of money if captured, but nothing if he was killed. For this reason, the practice of ransom contributed to the development of heraldry, which allowed knights to advertise their identities, and by implication their ransom value, and made them less likely to be killed out of hand. Examples include Richard the Lion Heart and Bertrand du Guesclin.