Crusading movement

The crusading movement encompasses the framework of ideologies and institutions that described, regulated, and promoted the Crusades. The crusades were religious wars that the Christian Latin church initiated, supported, and sometimes directed during the Middle Ages. The members of the church defined this movement in legal and theological terms based on the concepts of holy war and pilgrimage. The movement merged ideas of Old Testament wars, that were believed to have had God's support, with New Testament Christocentrism. Crusading as an institution began with the encouragement of the church reformers who had undertaken what is commonly known as the Gregorian Reform in the 11th century. It declined after the Reformation began during the early 16th century.

The idea of crusading as holy war was based on the Greco-Roman just war theory. This theory characterized a "just war" as one with a legitimate authority as the instigator, waged with a valid cause and good intentions. The crusades were seen by their adherents as a special Christian pilgrimage – a physical and spiritual journey authorized and protected by the church. They were acts of both pilgrimage and penance. Participants were considered part of Christ's army and demonstrated this by attaching crosses of cloth to their outfits. This marked them as followers and devotees of Christ, referencing biblical passages exhorting Christians "to carry [their] cross and follow Christ". Everyone could be involved, with the church considering anyone who died campaigning a Christian martyr. This movement was an important part of late-medieval western culture: it impacted politics, the economy and wider society.

The original focus and objective of the crusading movement was to take Jerusalem and the sacred sites of Palestine from non-Christians. These locations were pivotal for the inception of the First Crusade and the subsequent establishment of crusading as an institution. The campaigns to reclaim the Holy Land were the ones that attracted the greatest support, but the crusading movement's theatre of war extended wider than just Palestine. Crusades were waged in the Iberian Peninsula, in northeastern Europe against the Wends, and in the Baltic region; other campaigns were fought against those the church considered heretics in France, Germany, and Hungary, as well as in Italy against opponents of the popes. By definition, all crusades were waged with papal approval and through this reinforced the Western European concept of a single, unified Christian church under the Pope.