Louis IX and the Triumphal Cross of Constantine

This article examines the material and ideological meaning of the three relics of the True Cross acquired by Louis IX in 1241 and 1242, which were venerated, along with the Crown of Thorns, in the Sainte-Chapelle, as part of the broader project of building Capetian sacral kingship in the High Middle Ages. Although cross relics flooded Western Christendom after 1204, these three relics, acquired directly from the Byzantine emperor, were specifically associated with Constantine and Heraclius and their historic military victories against enemies of Christian empire. The article identifies one of the three relics, known to contemporaries as the crux triumphalis in Latin and the croix de victoire in French, which Byzantine emperors were said to have carried into battle, as a relic that Louis IX then brought with him on his crusade of 1249–50 to Egypt, in hopes of martialing its historic power against the infidel in battle.