The idea of holy war originates in the Old Testament, with the conquest of the Promised Land by the Israelites in the time of Joshua, ordained and directed by God. When his people are loyal to him, God facilitates their victories by unleashing forces only he can control, such as earthquakes, hornets, and celestial armies; Jehovah is held to be the sole protector of the Israelites, whose rebellions he chastises by subjecting them to the rule of gentiles.
These ideas of ethnic exclusivity are completely overturned in the New Testament: now the elect are those who, without distinction of race, accept Jesus Christ as their Savior. The Kingdom of God does not belong to this world and will not be established by force. It will be accomplished by God himself at the end of time, when Jesus will come down from heaven to destroy once and for all the forces of evil led by the Antichrist. Christ preaches a religion of love extended to all, and his disciples take no interest in worldly quarrels, which Jesus condemns in both word and deed. In his Sermon on the Mount, he refines the Mosaic Law, extending the idea of one’s neighbor to include all of humankind, and advocating a morality in which intention plays an important part: not only is it wrong to kill, but even anger and animosity should be banished. Even when acclaimed in Jerusalem as “king” and liberator of the Jews from Roman occupation, Jesus refuses to take any political actions; he chooses not to defend himself when arrested and forbids his disciples to defend him: “For all they that take the sword shall perish with the sword” (Matt. 26:52). Found guilty and sentenced, he prays for those who nail him to the Cross.
Over the next three centuries Christians followed this teaching and practiced nonviolence: when persecuted, they did not attempt to defend themselves, but either fled, or allowed themselves to be arrested and sentenced. They generally refused to do military service, to avoid having to kill others, but otherwise tried to be good citizens of the Roman Empire. According to the Christian leader Hippolytus of Rome (d. 235), Christians should not become soldiers, while those soldiers who became Christians should undertake not to kill, even if ordered to do so by their commander. According to the theologian Origen (d. 253/254), their prayers were of more use to the empire than their arms.
With the conversion to Christianity of Emperor Constantine I (the Great) in 312, perspectives shifted dramatically: the Christian Church was now favored, and the ensuing phenomenon of mass conversions led to less intense faith among believers, as well as a greater division between the clergy and their lay followers. Faced with the threat of barbarian invasions, Christians, by this time a majority, were forced to take up arms to defend the empire and civilization. The church began to excommunicate laymen who refused to take up arms, as, for example, at the Council of Arles (314), although the clergy, by contrast, were required to abstain from shedding blood.
St. Augustine of Hippo (d. 430) argued that one could still find favor with God by pursuing a military career, citing the biblical wars of the Lord as evidence. Morally acceptable wars still existed, even if they were not directed by God. Without actually developing a full-fledged theory of just war (which was to be the task of canonists of the twelfth and thirteenth centuries), Augustine laid down the foundation of the future doctrine of a just war: it should be declared by a legitimate authority (the emperor); it should be undertaken for morally acceptable reasons (such as the recovery of stolen property, the reestablishment of justice, or protection of the population against invaders); and it should be carried out by soldiers without hatred or personal interest in the conflict. If this was the case, the soldier who killed under orders was not committing homicide. Despite the influence of Augustine’s doctrine, medieval penitentials for a long time reflected older attitudes: a soldier who killed in a “public” war had committed a sin and had to do penance for it.
The breakdown of political unity after the collapse of the Roman Empire obscured the definition of legitimate authority: the idea of the state lost its influence, to be replaced by personal allegiances. The church became the primary ideological point of reference. This shift prematurely ended the incipient legal concept of the just war. Yet the use of arms was more than ever necessary in a fragmented medieval society dominated by aristocrats and warriors, in which the church itself required protection. This situation resulted in a progressive ideological glorification of certain wars, which led to the development of the concept of “holy war,” which up to that time had been alien to Christianity.
Several factors contributed to this doctrinal revolution, which in the course of a millennium took the church from pacifism to the crusade. The first of these was already in existence: the glorification of the defense of one’s country. Self- evident in the age of the Christian Roman Empire, it dwindled in importance after the establishment of the barbarian kingdoms in the West. Yet it reemerged when Clovis, king of the Franks (d. 511), a convert to Christianity, chose to champion the Roman Catholic form of Christianity against the Arianism of the other barbarian kingdoms and forged an alliance between the Merovingian monarchy and the papacy. The idea gained in importance under the Carolingian dynasty, which rose to power with papal support: Charlemagne (d. 814) styled himself the renovator of the empire and protector of the church and of “Christendom,” a concept that was still in the process of formation.
The task of protection of ecclesiastical personnel and property against the Norman invaders and against neighboring lay lords gave a new dimension to the idea of the sanctification of warriors fighting for the church. The movement known as the Peace of God demonized and anathematized warriors (Lat. milites) who despoiled church property, but praised those who protected it. Tales of miracles highlighted the violent punishments inflicted by the patron saints of monasteries upon those who caused damage to them; they glorified those who, led by the saints themselves, fought to defend them. The church blessed their weapons and their banners. Warriors fighting for the church were thus the object of a genuine sanctification, which was evident in the liturgy, in particular in the investiture rituals of lay advocates of monasteries (Lat. advocati) and of defenders of churches (Lat. defensores et milites ecclesiae).
This trend intensified when the papacy was threatened by enemies deemed to be “pagans,” and thus easy to demonize, notably Vikings and Saracens. The monarchical development of the papacy encouraged it increasingly to identify its own interests with those of the entire church, or even of Christendom as a whole; this identification brought about a greater sanctification of battles fought on its behalf, as well as the development of doctrinal elements characteristic of holy war: spiritual rewards for the living and the status of martyrs for those who had been killed. These elements had existed from the very beginning of the Islamic concept of holy war (Arab. jihād), and they now appeared in Christianity at the time when Islam threatened Rome. In 846, faced with a Muslim raid, Pope Leo IV called upon the Frankish warriors with spiritual promises: to those who died in battle to protect Rome “the heavenly kingdom would not be denied” [Epistolae Karolini aevi, vol. 3, ed. Ernst Dümm- ler (Berlin: Monumenta Germaniae Historica, 1899), p. 601]. Pope John VIII renewed this promise in 879.
The sanctification of warfare, either on behalf of the papacy or against the Muslims, did not cease with the end of the Muslim threat to Rome. The idea of holy war that eventually led to the crusades came about through the conjunction of two factors: the consolidation of papal authority as a result of the Gregorian Reform movement, and the beginnings of Christian reconquest in the West. In its battle for preeminence, the church reform movement of the eleventh century demonized all of its adversaries: heretics, “schismatic” clergy, and rebellious lay powers, as well as Muslims. Conversely, it praised and sanctified those who fought against them. Thus, in 1053 Pope Leo IX claimed to have had a vision of how soldiers who died fighting for him against the Normans at Civitate shared in the rewards of saints and martyrs. Thereafter various ecclesiastical writers stressed the merit of their struggle, emphasizing the heavenly rewards that accompanied it. In 1075 a knight named Erlembald, who had been killed in combat during the struggle of the reform party of Milan (known as the Pataria) against the “schismatic” (i.e., traditionalist) clergy of the archbishopric, was called a “soldier of Christ” (Lat. miles Christi), an expression that, after 1095, referred to crusaders. Erlembald was regarded as a martyr, miracles occurred at his tomb, and Pope Urban II beatified him shortly before the beginning of the First Crusade. The canonist Bonizo of Sutri saw him as a hero waging “the war of the Lord” (Lat. bellum domini), an expression borrowed from the Old Testament. The idea of holy war had made its appearance.
These ideas continued to manifest themselves when the enemies of the church were Muslims, who were identified with the pagans of earlier struggles. The fight against Islam, particularly in the Iberian Peninsula, thus took on the characteristics of a sanctified war of reconquest. As early as 1035, the chronicler Ralph Glaber related that monks who had been killed after having taken up arms to defend the population against the attacks of the vizier al-Mansûr (c. 1000) had gained the status of martyrs and been admitted into paradise. Pope Alexander II, perhaps in the context of the Bar- bastro expedition (1064), encouraged the clergy to help those who, “inspired by God,” decided to go to Spain; he lifted their penances and granted them absolution of their sins. Around 1073, Pope Gregory VII encouraged the French nobleman Ebalus of Roucy to go and liberate lands occupied by Muslims in Spain in order to restore the legitimate rights of St. Peter there. Pope Urban II, too, glorified and sanctified the reconquest in Iberia. According to him, Muslim rule was a temporary punishment inflicted by God upon his people and was nearing its end: the Christian reconquest thus had to continue in Spain, Sicily, Corsica, and the Near East. This armed reconquest was for him a pious and worthy enterprise, to be undertaken by princes as a penance. Writing to the princes of Catalonia, the pope encouraged them to recover the city of Tarragona rather than go on a pilgrimage to distant Jerusalem. Thus, military action linked to the reconquest of Spain was thought to be holy enough to be prescribed in atonement for sins, that is, as a penance; it was also considered as equivalent to the most prestigious of pilgrimages, that to Jerusalem.
For Pope Urban II, the reconquest of Iberia from the Muslims was just as holy an undertaking as the crusade for the liberation of Jerusalem that he proclaimed in 1095. He stated this in letters to Peter, bishop of Huesca, and to the Catalans, between 1096 and 1099; in them he emphasized the praiseworthiness of this reconquest, stating that the two wars against the Muslims, in Spain and in the East, were equally meritorious. Previously Pope Gregory VII had expressed in several of his letters his intention of personally leading an army to rescue the Christians of the East, driving out the Muslims, and liberating the Holy Sepulchre, accompanying this call with promises of spiritual rewards (1074). Urban II developed this idea by recommending the crusade to warriors as a penitential expedition, thus laying the foundations for the doctrine of indulgences that developed in the twelfth and thirteenth centuries. From 1095, however, the preaching of the crusade testified to the fact that the church had accepted the idea of holy war. It was regarded as meritorious, was recommended by preachers as a penance through which one could atone for one’s sins, and was thought to guarantee a place in Heaven to those who died in it, since they became martyrs for the faith. The diversification of crusading would later lead to a greater popularization of the idea of holy war. However, for the medieval church the crusade to the Holy Land remained the most commendable of all holy wars. At one and the same time it was a pilgrimage and a war sanctified by both the religious authority that proclaimed it (the pope) and by its aim, the liberation of the Holy Sepulchre, foremost among the holy places of Christendom.