Can ‘trauma’ be an appropriate or insightful category of historical analysis for the study of the medieval past? In this article I consider how trauma theory can expose links between representation, memory and violence during the period of the crusades. I focus on one case study of ‘collective trauma’–the capture of a relic of the True Cross by the army of Saladin at the battle of Hattin in 1187. According to Christian commentators, the battle of Hattin was particularly brutal and its effects were long-lasting. Yet it was not the battle itself that was recorded by western commentators as particularly damaging. Rather, it was the capture during the battle of a piece of the True Cross, one of the holy land’s most precious relics, that was recorded by eyewitnesses, later chroniclers, artists and preachers as the most shattering aspect of this event. This article considers the loss of the True Cross as a moment of significant ontological rupture for the Christians of the west. I suggest that the relationship between individual experience and collective identifications that lay at the heart of crusading culture can be illuminated by paying attention to contemporaneous theories of cognition, memory, experience and suffering. In so doing I am asking how past peoples tried subjectively and collectively to make sense of devastating experiences and how modern historians of the Middle Ages might usefully integrate trauma theory into historical method.