Achilles his armour

Macedonia as a whole tended to remain in isolation from the rest of Greece.

... for the first time he [Philip] began to understand how Macedonia's outdated institutions of feudalism and aristocratic monarchy, so despised by the rest of Greece, might prove a source of strength when dealing with such opponents.

In less than four years he had transformed Macedonia from a backward and primitive kingdom to one of the most powerful states in the Greek world.