Pope Alexander II developed a system of recruitment via oaths for military resourcing that Gregory VII extended across Europe. Christian conflict with Muslims on the southern peripheries of Christendom was sponsored by the Church in the 11thcentury, including the siege of Barbastro and fighting in Sicily In 1074 GregoryVII planned a display of military power to reinforce the principle of papal sovereignty. His vision of a holy war supporting Byzantium against the Seljuks was the first crusade prototype, but lacked support. Theologian Anselm of Lucca took the decisive step towards an authentic crusader ideology, stating that fighting for legitimate purposes could result in the remission of sins.