Framework of Christian holy war
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 11thcentury. 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.
Major features.
Historians trace the beginnings of the crusading movement to the changes enacted within the Latin church during the mid and late 11th century. These are known as the Gregorian Reform, from a term popularized by the French historian Augustin Fliche. He named the changes after one of the leading reforming popes, Gregory VII. The use of the term oversimplifies what was in fact numerous discrete initiatives, not all of which were the result of papal action.
A group of reformers took control of the governance of the church with ambitions to use this control to eradicate behaviour they viewed as corrupt. This takeover was initially supported by the Holy Roman Empire and by Emperor Henry III in particular, but went on to lead to conflict with his son, Emperor Henry IV. The reformers believed in papal primacy, meaning the Pope was the head of all of Christendom as heir of St Peter. Secular rulers, including the emperor, were subject to this and could be removed.
The reformist groups opposed previously widespread behaviour such as the sale of clerical positions and clerical marriage. The changes were not without opposition, causing splits within the church and between the church and the emperor. However, the reform faction successfully created an ideology for the men they saw as God's agents. From the second half of the 11thcentury, it empowered them to reshape the church according to the moral and spiritual principles they upheld. Historians consider that this was a pivotal moment, because the church was now under the control of men who supported a concept of holy war and would plan to make it happen.
The reformers now viewed the church as an independent force with God-given authority to act in the secular world for religious regeneration. The creation of the institutions of crusading were a means by which the church could act militarily with the support of the armed aristocracy. This would in turn lead to creation of formal processes for the raising of armed forces through which the church could enforce its will. While these fundamentals applied the crusading movement flourished, when they ceased to be significant the movement declined.
Penance and indulgence.
Before the crusading movement was established, the church had developed a system that enabled Christians to gain forgiveness and pardon for sins from the church on behalf of God. They did this by demonstrating genuine contrition through admissions of wrongdoing and acts of penance. In the latter part of the 11thcentury, Christianity's requirement to avoid violence was still a significant issue for the warrior class, so Gregory VII offered them a potential solution. This was that they too could have their sins forgiven if they supported him in fighting for papal causes, but only if this service was given altruistically. When Urban II launched the First Crusade at Clermont in November 1095, he made two offers to those who would travel to Jerusalem and fight for control of the sites Christians considered sacred. Firstly, those who fought would receive exemption from penance for the sins they committed. Secondly, while they were on crusade, the church would protect their property from harm. The enthusiasm of the crusading movement was a challenge to what had been conventional theology. A letter from Sigebert of Gembloux to Robert II, Count of Flanders, illustrates this point. Sigebert criticises Pope Paschal II and congratulates Robert on his safe return from Jerusalem but pointedly omits any reference to the fact that Robert had been on a crusade.
Later popes developed the institution further, declaring that crusaders would not only avoid divine punishment for their sins, but that their guilt and the sins themselves would be expunged. This was achieved by the church granting what was called a plenary indulgence. Calixtus II extended the same privileges and protections of property to crusaders' relations. Innocent III reinforced the importance of the oaths crusaders took. He also emphasised the view that the forgiveness of sin was a gift from God, not a reward for the suffering endured by the crusader while on crusade. It was in the 1213 papal bull called that he reached out beyond the noble warrior class, offering all Christians the opportunity to redeem their vows without going on crusade. The unforeseen consequence of this was the creation a market for religious rewards. Later, this scandalized some devout Christians and thus became a catalyst for the 16thcentury Reformation. At that time, some writers continued to seek atonement for their sins through the practice of crusading while John Foxe (the English martyrologist) and others saw this as "the impure idolatry, and profanation" 
Popes continued in the practice of issuing crusade bulls for generations, but Alberico Gentili and Hugo Grotius created an international rule of law that was secular rather than religious. The wars against the Ottoman Empire and in defence of Europe were conflicts on which Lutherans, Calvinists, and Roman Catholics could agree in principle. So the importance to recruitment of the granting of indulgences became increasingly redundant and declined.
Christianity and war.
The 4th-century theologian Augustine of Hippo Christianized Graeco-Roman theories of or just war. In the 11th century, canon lawyers extended his thinking to create the paradigm of Christian ('holy war'). This theory was based on the idea that if it met three criteria Christian warfare could be justified even though it was considered a sin. Firstly, it must be declared by an authority that the church considered legitimate. Secondly, the war must have defensive objectives or to be for the recovery of stolen property and rights. Lastly, the intentions of those taking part must be good. Using this justification the church supported various Christian groups in conflicts with their Muslim neighbours at the borders of Christendom. In what is now Northern Spain, encouragement was given during the siege of Barbastro; the Italo-Normans of Southern Italy were supported in their conquest of the Emirate of Sicily and in 1074 Gregory VII planned to lead a campaign himself in support of the Byzantine Empire. He was unable to gather the necessary support, possibly because his personal leadership was unacceptable. Despite this, his plans left a template for future crusades, as did the campaigns in Spain where leading thinkers and fighters developed practical and fundamental arguments for the crusading movement.
Around 1083, the thoughts and writing on these theories were consolidated into or "Collection of Canon Law" by Anselm of Lucca. Thomas Aquinas and others extended these theories in the 13thcentury into a concept of religious war. This enabled various popes to use canon law in the call for crusades against their enemies in Italy. The argument was that Rome was the estate of St Peter, so the popes' Italian campaigns were considered defensive and fought for the preservation of Christian territory. 
The thinking of church on these themes combined two ideas in the creation of crusading, one from the Old Testament and one from the New Testament. The first was that the wars of the Jews were believed to have been instigated by the will of God. The second was the Christocentric ideas related to Christians forming individual relationships with Christ that came from the New Testament. In this way the church was able to combine the ideas of holy war and Christian pilgrimage to create the legal and theocratic justifications for the crusading movement. The historian Carl Erdmann mapped out the three stages for the argument creating the institution of the crusading movement:
Knights, chivalry and the military orders.
Innovations in military technology and thinking made the first crusades feasible. Military tactics developed to utilize heavily armoured cavalry and control of society was achieved by the development of castles. These required men for garrisons, the extensive training or which in turn created new social mores and led to the rise of combat as sport. At sea increasingly large navies were deployed, built by Italy's maritime republics. At this time although knights were praised in literature they remained distinct from the aristocracy. Crusading and chivalry developed together, and in time chivalry helped shape the ethos, ideals and principles of crusaders. Tournaments were held where knights could exhibit their martial prowess. This provided venues where the crusading movement could recruit, spread propaganda and announce the recruitment of senior figures. However, even though crusading knights and some notable commanders demonstrated courage and commitment in military terms the campaigns in the Levant were not typically impressive. In feudal Europe, the formation of disciplined units was a significant challenge, strategic approaches and institutional frameworks were underdeveloped, and power was too fragmented to support cohesive organisation.
Literature presented the exemplar of an idealized, perfect knight in works such as Roman d'Alexandre written around 1130. These works celebrated adventure, courage, charity, and refined manners. However, the Church could not fully embrace all of these values they promoted. Its' spiritual views contrasted with ideas of excellence, achieved glory through military deeds and romantic love. While the church feared the warrior class, it still needed to co-opt its power and demonstrated this symbolically through the development of liturgical blessings to sanctify new knights. In time, kings represented themselves as members of the knighthood for propaganda purposes and crusading became to be seen as integral to the ideas of this ideal. From the time of the Fourth Crusade, crusading became an adventure normalized in Europe, thus creating a divide between the knights and other social classes and altering the relationship between knightly adventure, religious, and secular motivation.
In the polities created by the crusading movement in the Eastern Mediterranean known as the Crusader states the creation of military religious orders was one of the few innovations from outside Europe. In 1119 a small band of knights formed to protect pilgrims journeying to Jerusalem. These became the Knights Templar and many other orders followed this template. The Knights Hospitaller were already providing medical services to which was added a military wing leading to a much larger organisation. These orders became Latin Christendom's first professional fighting forces and played a major part in