In about 55292 a boy named Muhammad bin ‘Abd Allah was born into a minor clan of the tribe of Quraysh, which was settled in and around the shrine centre of Mecca in the Hijaz, about 900 kilometres south of Syria. A trader by profession, he participated in the caravan trade of Arabia and visited Syria on several occasions. In about 610 he began to preach a monotheistic faith called ‘submission to God’, or Islam, and summoned his fellowMeccans to prepare for the Last Judgement. By 622 difficulties in Mecca and the erosion of vital support had reached the point where he was obliged to move to Yathrib, 300 kilometres to the north. This migration (the hijra)93 proved to be of crucial importance: for in Yathrib, henceforth calledMedina,94 the ranks of his followers increased dramatically. Raids on enemy caravans, camps and villages met with success and further expanded his support. Muhammad returned to Mecca in triumph in 630, and by the time of his death two years later his authority extended over much of Arabia. The rest was brought under control by the first caliph, Abu Bakr (632–4), andMuslim forces went on to campaigns of conquest that, in less than a century, created an empire extending from Spain to Central Asia. How all this occurred and why it focused onMuhammad,Mecca and the late sixth century are questions that early Muslims took up themselves,95 and they are a major concern of modern historical research. In the 1950s William Montgomery Watt proposed a socio-economic solution. Mecca was a major centre for overland caravan trade, and its merchants and others grew wealthy on the profits from commerce in such precious items as incense, spices, gemstones and gold. This widened the gap between rich and poor and led to social malaise as crass materialism eroded traditional values. Muhammad’s message was essentially a response to this crisis.96 More recently, however, serious challenges have been made to the notions of a lucrative Arabian trade in luxury items, of Mecca as an important entrepot, and hence of some serious crisis provoking a religious response.97 Mecca is not mentioned in any non-Arabic source of the pre-Islamic period, and does not lie on the main communication routes in western Arabia. The site itself is barren, inhospitable and incapable of sustaining agriculture for more than a minuscule population. Even had there been a lucrative international trade passing through the Hijaz in the sixth century, it would not have found an attractive or logical stopping-point at Mecca, which owed its success to its status as a shrine and pilgrimage centre. As at certain other shrines in Arabia, pilgrims came to circumambulate a rock – in this case associated with an unroofed building called the Ka‘ba – and to perform religious rituals with strong affinities to those of Judaism: these included offerings and animal sacrifice, washing and concern for ritual purity, prayer and recitation of fixed liturgies.98 There are indications that, early on, few people were resident at the site: ‘People would perform the pilgrimage and then disperse, leaving Mecca empty with no one living in it.’99 The success and expansion ofMecca were due to the administrative and political skills of its keepers, the tribe of Quraysh. The Ka‘ba seems to have been a shrine of the god Hubal,100 but in the religiously pluralistic milieu of pagan Arabia it must not have been difficult to promote it as a place where other deities could be worshipped, too. A greater achievement was convincing other tribes to honour the sanctity of theh. aram of Mecca and to suspend raiding during the sacred months when pilgrims came. As agriculture was not possible at Mecca, Quraysh had to bring in food from elsewhere and so was at the mercy of nearby tribes in any case. The very fact thatMecca survived, much less prospered, thus reflects the diplomatic skills of Quraysh. The Islamic tradition, of course, makes much of the a priori importance of Quraysh, but this is surely something that emerged within the paradigm of a sedentary tribe seeking to protect and promote its interests through skilful manipulation of relations with the nomadic tribes around it. There was mutual advantage in the prosperity of Mecca: trade with pilgrims, import and marketing of foodstuffs and other necessities, and collection and distribution of taxes levied in kind for feeding and watering pilgrims.101 It may even be that Quraysh was able to organise a profitable trade with Syria, perhaps as a result of disruption to the agricultural productivity of the Levant caused by the destruction of the Persian wars, numerous droughts in Syria,102 and the repeated visitations of bubonic plague after 541.103 The message that Muhammad preached in the milieu of a prosperous Mecca was in many ways a familiar one, and in others quite a novelty.104 His summons to the worship of oneGod recalled the notion of a ‘high god’, and his identification of Islam as the religion of Abraham had important associations with the doctrines of h. anfya. As can be seen from the testimony of Sozomen, his call for the restoration of a pristine faith, free from the corruptions that had crept into it, was already a time-honoured tradition in Arabia. The observances he advocated were also well known from either pagan Arabian or Jewish practice: prayer and Friday worship, fasting, pilgrimage, ritual purity, almsgiving, circumcision and dietary laws.105 WhereMuhammad broke with tradition was in his insistence on absolute monotheism and his advocacy of a relationship with God that abandoned traditional pragmatic views of religion and summoned man to unconditional commitment and faith in response toGod’s creative munificence and continuing solicitude. The rejection of pagan eclecticism, however, threatened the entire social and economic position of Quraysh and thus earned him the enmity of their leaders. Among the public at large his message – with its corollaries of reward and punishment in the hereafter – seemed extreme and delusory and evoked little positive response.106 In order to gain support Muhammad had to prove that his God was a winner, and this he achieved by moving to Medina, where he used his expanding following to disruptMeccan commerce and food supplies.107 His military success made him a force to be reckoned with: the tribal arrangements so carefully nurtured by Mecca over the years soon fell apart in the face of this challenge, while the victories of the new religion provided the worldly success which Arabs demanded of their gods and also appealed to the Arabs’ warrior ethic. Islam also had a broad appeal on other grounds. The Koran presented itself as a universal scripture ‘in clear Arabic speech’,108 and thus took advantage of the position of the Arabic language as the common cultural tongue of Arabia and a basis for common action.109 Arabs could also identify with one another, despite their tribal distinctions, on the basis of a shared participation in Arabian tribal organisation and custom, a heritage of similar cultural and religious experience in pagan systems and folklore, and a long history of trade and commerce, revolving around fairs and religious shrines, that engendered a certain feeling of familiarity around the peninsula. It has often been asserted that the Arab conquests were of essentially Islamic inspiration. The Islamic tradition of spreading theWord sees things this way, and the Armenian chronicle, written in the seventh century and attributed to Bishop Sebeos, also has Muhammad urging his followers to advance and claim the land promised to them by God as the descendants of Abraham.110 It therefore seems probable that there was a religious agenda to the conquests from the start, and it is certainly true that without the unifying factor of Islam there would probably have been no conquest at all. But the arguments of leaders and advocates are one thing, and the response of the fighters themselves is another. Even in Mecca and Medina the teachings of Muhammad and the text of the Koran were still known in only fragmentary fashion, and it is difficult to see how most tribesmen elsewhere could have had more than a vague and trivial knowledge of either so soon after the Prophet’s death. Many warriors who joined the conquest forces had only recently fought against the Prophet himself, or had resisted the efforts of the first two caliphs to bring Arabia under their control. It is also implausible that tribal warriors all over Arabia could so quickly have abandoned the pragmatic and worldly attitude towards religion that had prevailed for centuries, in favour of one that expected genuine commitment to the one God. There is, in fact, good evidence on the conquests showing that this was not the case at all.111 This is not to detract from the centrality of the message of Islam to Muhammad’s own sense of mission and purpose, and probably to that of others around him. One may also concede that Islam enabled the Muslim leadership to mobilise warriors in a way that transcended important differences, and it is likely that Islamic slogans and admonitions of various kinds were often inspiring to fighters on the ground. But if the faith played an important role in uniting and mobilising the tribes, it was nevertheless waves of tribal forces, motivated primarily by traditional tribal ambitions and goals, that broke over Syria, Iraq and Egypt from the 630s on. It is unlikely that either Syria or Iraq could have withstood the advance of forces of this kind, given the state of their defences after the end of the last Persian war in 628, only six years before the first Arab advance. The Arab armies were not simply marshalled inMedina and then sent forth with the caliph’s instructions; providing food, fodder and water for an army of thousands of men and animals would have been extremely difficult. The norm was rather for small contingents to expand as other groups gradually joined them on the march; the sources make clear that commanders were expected to engage in such recruiting along the way, to ensure that the newcomers were armed and equipped, and to ‘keep each tribe distinct from the others and in its proper place’.112 In this way a small force could soon swell to thousands as warriors joined its ranks in expectation of adventure, fighting and plunder. The situation was made more difficult by the fact that confronting the Arabs on this scale posed entirely new military problems. Both imperial powers were accustomed to dealing with Arabs as bands of raiders, and had planned their frontier defences accordingly. Watch-towers and forts, many of them abandoned for centuries in any case, were inadequate to deter the forces that now swept past them, and whereas the old Roman system had anticipated incursions by single uncoordinated bands, it was now confronted by penetration at many points simultaneously. It was probably also difficult to determine exactly where the enemy was at any given time, for when battle was not imminent an Arab army tended to fragment into bands of warriors roaming the countryside. Finally, and as the above example shows, Arab strategy was often highly reactive and thus difficult to counter or predict. Incursions into Iraq, for example, seem to have begun when drought in Arabia obliged the tribe of Rabi‘a, of the Banu Shayban, to migrate into Iraqi territory, where the Sasanian authorities permitted them to graze their herds on the promise of good behaviour. But the presence of these tribal elements eventually led to friction, which the Rabi‘a quite naturally interpreted as unwarranted reneging on an agreed arrangement. When they called on their kinsmen elsewhere for support, the crisis quickly escalated into full-scale conflict between Arab and Persian forces.113 It is difficult to guess whether either of the great powers would have been able to stem the military momentum that was building in Arabia, even had they correctly gauged the threat it posed. With Kinda, the Ghassanids and the Lakhmids all in a state of either collapse or disarray, the growing strategic power of Islam was able to develop in what otherwise amounted to a political void; the real source of the danger confronting the empires was effectively beyond their reach from the beginning. Byzantium and Persia could fight armies that violated their frontiers, but could not stop the process that was generating these armies in the first place. Initial victories over the Arabs atMu’tah in Syria in 632 and the battle of the Bridge in Iraq in 634 thus proved no deterrent, as in earlier times would have been the case.114 What overwhelmed the Byzantines and Sasanians was thus the ability of the message and charismatic personality of Muhammad to mobilise the tribal might of Arabia at a level of unity never experienced among the Arabs either before or since. Unprepared for defence on the scale required to counter this new threat and unable to marshal tribal allies of their own to strike at their foe in his own heartlands, both were forced to fight deep within their own territories and suffered defeats that simply encouraged further incursions on a larger scale.Greek and Persian field armieswere crushed in one disastrous battle after another, leaving cities to endure sieges without hope of relief and encouraging resistance everywhere else to evaporate in short order.