Despite Christ's injunction to his disciples to refrain from swearing oaths, oaths and oath-taking were a fundamental element of medieval Christian culture. Oaths ‘served as a method of proof and a guarantee of truth in legal process and social life’, whether this was the truth of a statement, such as the testimony of a witness in court, or the truth of a promise to undertake some course of action, such as wedding vows. The medieval aristocracy, both lay people and clergy, was acutely aware of the importance of oaths. Vassals swore an oath of homage to their lord, monks swore an oath of obedience to their abbot and clerics to their superiors in the Church hierarchy.

The most common Latin words for oath were iusiurandum and iuramentum, deriving from ius (right or law), which indicate their legal nature, and sacramentum, from sacrum (sacred), indicates their connection with the spiritual and divine. Canon lawyers were unanimous that oaths fell under ‘natural’ or divine law, as the violation of an oath was a crime against God, who was invoked as a witness to its content. Oath-taking rituals frequently involved the swearer making physical contact with a scared object, such as a Gospel book or relic. Contemporaries made a distinction between this kind of solemn oath, which invoked the divine, and other promises. There was also powerful social pressure on people to keep their oaths: oath-taking often formed part of public rituals and witnesses were expected to ensure that its terms were adhered to. An oathbreaker would lose face before their peers and be ostracised from normal social relations, as one who could not be trusted to keep their word.

In the context of medieval warfare, combatants would make agreements with their opponents, usually to observe a truce, suspending hostilities for a given period for a parley or other reason. This was a generally accepted custom, similar to the granting of a conditional respite to a garrison or surrendering a stronghold when there was no prospect of mounting an adequate defence. It can be difficult to determine precisely what was said in a given situation and what oaths, if any, were sworn.