ABSTRACT
The creation within the space of a single century of a vast Arab Empire stretching from Spain to India is one of the most extraordinary marvels of history. The speed, magnitude, extent and permanence of these conquests excite our wonder and almost affront our reason, but the historian who seeks to explain them is impeded by the deficiency of the evidence at his disposal. Few revolutions of such gigantic import are worse documented: the conquerors were an unlettered people; the archives of Persia perished in the general ruin of the Sassanid State, and the Greek side of the story is revealed only in chronicles put together nearly two centuries after the irruption of Islam into the eastern provinces of Byzantium.
