In the Hellenistic period, as in earlier periods, war was a presence always felt in the Greek world, not only because it happened but also because of its widespread impact upon modes of organization and expression. But clearly, we cannot possibly consider every aspect of war in a short section and shall have to confine our study here to the subject of the armies as they exercised their specifically military functions. We shall furthermore assume that the decisive changes brought about in the reigns of Philip and Alexander in this sphere are already familiar to the reader.

In size the Hellenistic armies equalled those which had taken part in the conquest of the Persian kingdom. This was true at least in the kingdoms that had emerged following the break-up of Alexander's empire, although the old Greek cities usually found it hard to assemble forces comparable with those of the classical period. The sovereigns of the new kingdoms in effect went into decisive battles with about 60,000 men. Some were even in a position to raise 100,000: Antiochus III, for example, in the expedition that set out for central Asia. To these forces must be added ‘those who were part of the baggage’ (aposkeue), that is to say the heterogeneous assortment of noncombatants (women, children, slaves, merchants and entertainers of every kind) who must have swelled the numbers by an average of perhaps half as many again as the armed forces. This kind of town on the move clearly posed delicate logistic problems from the point of view of contemporary levels of productivity and means of transport, and these problems largely determined the course of military operations.