The defeat of Bardylis ‘the king of the Illyrians‘ was one of the decisive battles of ancient history. It ended forty years of military ascendancy by the Illyrians, during which huge losses had been inflicted on the Molossians, Amyntas III had twice been driven out of Macedonia, and Perdiccas III and 4,000 Macedonians had been killed ‘in a great battle’ of359B.C.(Diod. 16.2.5). One reason for that ascendancy was that the Illyrians adopted Greek hoplite equipment and tactics earlier than their opponents. The victory of Philip marked the beginning of Macedonia’s progress to a military supremacy, of which the marks were the infantry fighting with the pike (sarissa) and the cavalry exploiting a break in an enemy line. Evidence about the battle is provided only by Diodorus andFrontinus, and there are uncertainties about the background to the affair. I think that progress can be made if we ask the appropriate questions.