God's War: A New History of the Crusades

name is called The Word of God. And the armies which were in heaven followed him… And out of his mouth goeth a sharp sword that with it he should smite the nations: and he shall rule them with a rod of iron: and he treadeth the winepress of the fierceness and wrath of Almighty God. (Revelation 19:11–15)

Such imagery and language as well as the martial history of the biblical Chosen People of the Old Testament fed directly the world-view of the crusaders, providing rich quarries alike for preachers and chroniclers. Although the surviving letters from the First Crusaders contain only one reference to the Apocalypse, commentators were full of it. In a notorious passage, Raymond of Aguilers, chaplain to Raymond IV, count of Toulouse, one of the leaders of the First Crusade, who witnessed the fall of Jerusalem in 1099, described the ensuing massacre on the Temple Mount: ‘it is sufficient to relate that in the Temple of Solomon and the portico crusaders rode in blood to the knees and bridles of their horses’.⁶ Whatever the atrocities performed that day, Raymond was quoting Revelation 14:20: ‘And the winepress was trodden without the city, and blood came out of the winepress, even unto the horse bridles.’ It is hard to exaggerate the dependence of Raymond’s contemporaries on the Scriptures for imagery and language. Many saw Urban II’s holy war as the fulfilment of biblical prophecy or an imitation and renewal of scriptural struggles. Just as the reformed papacy of the eleventh century loudly proclaimed its adherence to the so-called New Testament Petrine texts in which Christ committed His Church to St Peter, so the holy war itself was perceived and possibly designed to revolve around Matthew 16:24: ‘If any man will come after me, let him deny himself, and take up his cross, and follow me.’ This was the text referred to in the deal between the south-east German abbey of Gottweig and Wolfker of Kuffern, who had decided to join the march to Jerusalem in 1096 because ‘he wanted to fulfil the Gospel command, “who wishes to follow me”’.⁷

This process of translating the spiritual conflict described by St Paul into a doctrine of battle and reversing the habit of discounting the interminable wars of the Israelites as literal models for Christian behaviour was not sudden. Until the adoption of Christianity by the Roman state, public war had been rejected by theologians such as Origen of Alexandria in the third century, who insisted that the Old Testament wars should be read as allegories of the spiritual battles of the New Covenant. Thereafter, Christianity had to come to terms with more than biblical exegesis. In devising a tentative theoretical justification for war in the fourth and fifth centuries, the Church Fathers incorporated two distinct traditions of legitimate war, the Helleno-Roman and the Jewish.

The fourth-century bc Greek philosopher Aristotle coined the phrase ‘just war’ to describe the categories of acceptable warfare (Politics I: 8). War provided a natural form of acquisition for the state but should not be an end in itself. It could legitimately be deployed in self-defence, to prevent the state’s enslavement; to obtain an empire to benefit the inhabitants of the conquering state; or to enslave non-Hellenes deserving of slavery. The key was the justice of the ends for which the war was fought. In his Politics (VII: 14) Aristotle insisted that ‘war must be for the sake of peace’. There was no concept of a religious war per se nor of religious disapproval of war, as public religion resembled a civic cult, thus the needs of a virtuous state were almost by definition just. Even while Aristotle deplored the Spartan attitude of war for its own sake, Athenian just war in practice accommodated the tradition of victors’ genocide of those they defeated. To Aristotle’s just ends, Roman Law added just cause, a causa belli as the historian Livy put it, based on contractual relations. From the Latin for peace, pax, derived from the verb pangere, meaning to enter into a contract, it was argued that war was justified if one party was guilty of breaking an agreement or injuring the other. As a legal procedure, to jurists such as Cicero, just war required formal declaration and purposes of defence, recovering lost goods or punishment. The enemy of a just war was ipso facto guilty. Cicero also argued for right conduct, such as virtue or courage, in waging a just war. The practical consequences of these theories lent the aura of justice to all Rome’s wars against external enemies, especially barbarians, identified as hostes, public enemies, automatically legitimate targets of just war.⁸

CHRISTIAN JUST WAR

When Christianity became adopted as the official religion of the Roman empire in the early fourth century, Graeco-Roman just war confronted the Judaic tradition of wars fought for faith and not merely temporal but divinely ordained rights. The conversion of Constantine and the final recognition of Christianity as the offical religion of the Roman empire in 381 prompted the emergence of a set of limited principles of Christian just war which, by virtue of being fought by the Faithful, could be regarded as holy. The identification of the Roman empire with the church of God allowed Christians to see in the secular state their protector, the pax Romana being synonymous with Christian Peace. For the state, to its temporal hostes were added enemies of the Faith, pagan barbarians and, more immediately dangerous, religious heretics within the empire. Eusebius of Caesarea, historian of Constantine’s conversion, in the early fourth century reconciled traditional Christian pacifism with the new duties of the Christian citizen by pointing to the distinction between the clergy, immune from military service, and the laity, now fully encouraged to wage the just wars for the Christian empire. Ambrose of Milan (d. 397), as befitted a former imperial official, consolidated this symbiosis of the Graeco-Roman and Christian: Rome and Christianity were indissolubly united, their fates inextricably linked. Thus the war of one was that of the other, all Rome’s wars were just in the same way that those of the Old Testament Israelites had been; even heresy could be depicted as treason. Ambrose’s vision of the Christian empire and the wars to protect it which constituted perhaps the earliest formulation of Christian warfare was, therefore, based on the union of church and state; hatred of foreigners in the shape of barbarians and other external foes; and a sharp intolerance towards dissent and internal debate, religious and political.

The collapse of the institutions of the Roman empire in the west in the fifth century undermined Ambrose’s union of interests and could have threatened the whole theoretical basis of Christian just war without the work of a younger contemporary, Augustine of Hippo (d. 430). Augustine combined the classical and biblical doctrines of just war to arrive at some general principles outside the context of an active imperium Romana. Augustine’s analysis depended on sin, which caused war but which could also be combated by war. In the face of the political realities of successful barbarian invasions and Donatist heretics in his North African diocese, Augustine combined the Graeco-Roman ideas of right causes and ends with a Christian concept of right intent. With Aristotle he agreed that the right end of war was peace. With Cicero he argued, ‘it is the injustice of the opposing side that lays on the wise man the duty of waging war’. With Roman lawyers, he agreed that public war must be supported by authority, but cited scriptural evidence: ‘the commandment forbidding killing was not broken by those who have waged war on the authority of God’.⁹

From Augustine’s diffuse comments on war could be identified four essential characteristics of a just war that were to underpin most subsequent discussions of the subject. A just war requires a just cause; its aim must be defensive or for the recovery of rightful possession; legitimate authority must sanction it; those who fight must be motivated by right intent. Thus war, by nature sinful, could be a vehicle for the promotion of righteousness; war that is violent could, as some later medieval apologists maintained, act as a form of charitable love, to help victims of injustice. From Augustine’s categories developed the basis of Christian just war theory, as presented, for example, by Thomas Aquinas in the thirteenth century.

However, Augustine was no warmonger. The world of the spirit was preferable to that of the flesh. Although public prayers, litanies and masses continued to be said from the fifth to the eight centuries, especially under papal instigation in Rome itself, to invoke divine aid in wars against enemies of the church, the Christian tradition of withdrawal from the world, of non-violence and condemnation of temporal aggression remained, if anything strengthened by the spread of monasticism across Christendom. Nonetheless, Augustine had moved the justification of violence from lawbooks to liturgies, from the secular to the religious. His lack of definition in merging holy and just war, extended in a number of later pseudo-Augustinian texts and commentaries, produced a convenient conceptual plasticity that characterized subsequent Christian attitudes to war. The language of the bellum justum often described what came closer to bellum sacrum. This fusion of ideas might conveniently be called religious war, waged for and by the church, sharing features of holy and just war, allowing war to become valid as an expression of Christian vocation second only to monasticism itself.

A just war was not necessarily a holy war, although all holy wars were, to their adherents, just. While holy war depended on God’s will, constituted a religious act, was directed by clergy or divinely sanctioned lay rulers, and offered spiritual rewards, just war formed a legal category justified by secular necessity, conduct and aim, attracting temporal benefits. The fusion of the two became characteristic of later Christian formulations. Where