The crusades grew out of the papal reform movement, for they provided the papacy with a means to put its ideas about the regeneration and purification of society into practice. The formation of an army of God had a double advantage in that it provided a means of enforcing papal will and at the same time diverted the warlike activities of the most belligerent classes of society towards papal ends, instead of their preoccupation with internal feuding and attacks upon the clergy or clerical property. In its most dramatic form this entailed the recruitment of large armies to fight an external enemy which, it was claimed, had violently seized the Holy Places, the very sites of Christ’s life, death and resurrection, persecuted the Christian inhabitants, and erected idols in place of the worship of the true faith. However, the concept was more flexible than this. Gregory VII had already used papal armies against the enemies of the faith in Italy and had presented them as ‘soldiers of Christ’ and, although in the twelfth and thirteenth centuries the capture and defence of Jerusalem remained central to the Christian vision of the crusade, the instrument which the papacy had forged could be used in other contexts, apparently with equal validity. Indeed, the original idea of a Christian ‘just war’, formulated by St Augustine in the pre-Islamic era, necessarily conceived that such force would be used against those who would disrupt Christian society such as heretics, schismatics or men of violence.