Chivalry, or the chivalric code, is an informal and varying code of conduct developed between 1170 and 1220. It was associated with the medieval Christian institution of knighthood; knights' and gentlemen's behaviours were governed by chivalrous social codes. The ideals of chivalry were popularized in medieval literature, particularly the literary cycles known as the Matter of France, relating to the legendary companions of Charlemagne and his men-at-arms, the paladins, and the Matter of Britain, informed by Geoffrey of Monmouth's Historia Regum Britanniae, written in the 1130s, which popularized the legend of King Arthur and his knights of the Round Table. All of these were taken as historically accurate until the beginnings of modern scholarship in the 19th century.