Western scholars have understood the Islamic conquest in various ways. These include:
• Islam is a violent faith, which imposed itself at sword point. Conquered people, fearing death or expulsion, had to convert to Islam. This, the most widely held interpretation, has been recapitulated throughout the centuries, countless times.
• William Muir understood the Muslim conquest as a result of mass migration of Arabs, which was, in turn, caused mainly by the cupidity of tribesmen and their ‘love of rapine and the lust of spoil’.
• The mass migration of the Arabs was a result of a gradual process of desertification in the Arabian Peninsula.
• The Islamic expansion was born of an irresistible penchant for the raid, which animates all Arabs. The success of these tumultuous incursions, due to a superior military organization, suggested to them, as an afterthought, the idea of occupation and conquest, which was absent at the outset.
• In 1929 Carl Heinrich Becker wrote an essay on the Islamic expansion in which he called attention to the fact that the great migration of the Arabs took place only after the decisive victories of Muslims in Syria and Iraq. That is, the conquest of these areas preceded and unleashed the Arab migrations, not the reverse. These migrations, he believed, were stimulated by the promise of wealth and land in the conquered domains. Becker felt that religion was a force of secondary importance in stimulating the expansion; rather, hunger and greed provided the driving force behind the migrations.
• The causes of the conquest’s success were related to the general weakness of Byzantium and Sassanid Persia, because of their prolonged wars and the fortuitous presence of a large number of good generals and administrators on the Arab side.
• In a general study, which appeared in 1968, Francesco Gabrieli saw religion as an important factor, not because it unified the Arab tribesmen, but because it unified the elite, mainly Companions of the Prophet, who led the campaigns of conquest. Yet, equally, he referred to the important role of material motives (food, pastureland, booty) in encouraging emigration from Arabia.
Having cited all but the first of these opinions, Donner made a significant comment. He thought that a closer look at the received interpretations of Islamic conquest revealed an even more fundamental problem. For on examination, most of them viewed the conquest either as the result of some deterministic historical process, such as the pressure of increasing population in Arabia, or as the result of a fortuitous combination of historical accidents, such as the raids of undisciplined Arab tribesmen into the Fertile Crescent at a moment of temporary weakness in the Byzantine and Sassanid empires. In either case, these interpretations deny, in effect, that the ‘Arab conquest’ was in any organic way related to the appearance of Islam.