This doctoral dissertation aims to critically examine and clarify the significance of the theory of just war (bellum iustum) for the Crusade movement of the 11th and 12th centuries, as well as to more precisely determine its importance in comparison to other motives and strategies of justification. In doing so, it must be clarified what role a concept of justice shaped by the Church Father Augustine—specifically, his doctrine of just war—played in legitimizing the Crusades.

The medieval tradition of the concept of just war, as shaped by Augustine, offers two starting points for its application in the discourse on the Crusades: First, we must ask to what extent the notion of Jerusalem and the Holy Land as God’s property functions within this discourse as a justification for a just war. Second, we will examine, across various levels of discourse, to what extent the popes—with regard to the 11th- and 12th-century Crusades to the Holy Land—viewed and presented themselves as legitimate warlords in the sense of a “just” war. From this perspective, the aim is to determine more specifically to what extent the Crusade, as a just war authorized by the pope, had repercussions on the legitimization and acceptance of papal authority.

To this end, the study draws in particular on diplomas from the papal Propaganda and their reception in order to examine the strategies of legitimation contained therein. The material used for the analysis therefore consists primarily of diploma certificates and letters from popes, legates, and crusaders, as well as historiographical accounts. In examining these sources, one must ask what role a collectively symbolic construction of reality plays in the legitimation of the Crusades—or, conversely, to what extent such a reality was constructed through the discursive justification of the Crusades. Following Jürgen Link, “collective symbolism” is understood here as the “totality of a culture’s so-called ‘imagery’” (Jürgen Link: Versuch über den Normalismus. Wie Normalität produziert wird, Opladen 1997, p. 25). Thus, this study examines the extent to which the concept of a just war can also be found in the collective symbolism of the discourse on the Crusades and, in this respect, forms part of a so-called synchronous system of collective symbols. Subsequently, the focus will also be on the effect of binary reductionisms or binaries—such as, in particular, “just” and “unjust”—in legitimizing domination and power.