The difference in the number of combatants on each side is not necessarily a decisive factor in the course of military events. The quality of the personnel, the standard of weaponry, the capacity for tactical manoeuvring and the particular conditions of the battle site may cancel out or at least limit the importance of numerical superiority. Nevertheless, modern historians are wont to make the number of combatants the first piece of information given about rival armies and the course of a battle. In doing so they not only assume that quantity quite often becomes quality, but are following a prevailing historiographic tradition. Many a historian, of antiquity stressed the numbers because often their significance was more comprehensible to him than was that of other components of military might. In accordance with that time-honoured procedure, we shall open our re-examination of the sources and of scholarly views with a study of the question of the relative size of the forces.

A simplistic view of the importance of the numerical factor in the course of a battle led, in most ancient literature, to a distortion of the data. This feature is not only characteristic of Oriental literature, but is familiar from Classical and Hellenistic historiography. The exaggerated figures cited by most Greek sources, beginning with Herodotus, for the Persian armies up to and including the era of Alexander the Great, are notorious. Needless to say, writers who had no real information at all on the actual numbers let their imaginations soar.