Philip II became at the age of 22 governor in the name of the not fully grown son of his murdered brother. He did his job so well that soon he was chosen as king by the council of the army. As a member of the ruling class he had a Greek education and the political relations in Hellas were well known to him as he had several personal connections with Thebes, and as he could make use of Greek advisors, of whom the philosopher Aristotle the most famous one is.

Expansion of Macedonian territory.

He started his government with internal actions against tribes in the northern and eastern mountains who refused to recognize a central government. During the war against the Illyrians he found an ally in the house of Epirus. His later wife Olympias, who he married in 358, was a member of this house. In 357 Macedon had for the first time a conflict with Athens. Athens tried to restore her old empire as we know, and for this she needed Amphipolis and the mines in the Pangaeus mountains. Philip had been taking advantage of the disunity of the Greek cities to seize a string of northern places, including Amphipolis, and to acquire control of Thessaly with all its assets. The profits of the Pangeaus mines enabled him to expand the road network in his country.

The profits of the mines also enabled him to built up a permanent army. Because of this was he less dependent on the military support of kingdoms of Macedon. The permanent character of the army also guaranteed a high grade of training. The new Macedonian army was superior, quantitative and qualitative, to any Greek army. The phalanx was based on the sloped phalanx which was so successfully used by the Thebans during the battle of Leuctra. New factors were that the phalanx of pezheptairoi was supported on the sides by the heavy cavalry of the heptairoi, and that so-called peltasts, light-armed but highly mobile forces, supported the infantry and cavalry. The national character was also a strong point of the army of Philip II: recruitment took place at a regional basis. This improved the unity of the army dramatically. The commanders were nobles who formed a sort of elite around the king, like a heptairoi new style.

The different phases in the expansion of Philip's power were characterized by a brilliant diversity of political and military actions. Of course he was fortunate in the weakness of the states who should have been making it their business to confront him. Luckily for him the Greek Poleis did not form an unity and were to busy with their private preoccupations like they had done most of the time the last centuries: Athens second Naval Confederacy was torn apart during the Social War from 357 till 355, Sparta's efforts to restore its once formidable power by recovering domination of Messenia were futile, and Thebes involved in a war with Phocis.

The conquest of Hellas.

By 346 Athens' military struggle against Philip had achieved so little that a peace treaty between both was signed, the so-called Peace of Philocrates. Athens would give up any future attempts to regain control over Amphipolis. From Philip's point of view was the peace very useful. He now not only had peace, but also an alliance with Athens and he would need her navy, or at least the neutrality of her navy, for his future plans against Persia. Philip used the peace to reinforce his position in Thessaly and Thrace, while Demosthenes attempted to change the Greek opinion about the invasion of the barbarian. The peace would not be permanent however, and it is not known if the endlessly provocative Demosthenes or Philip was the reason for this.

Only at the last moment an alliance between Athens and Thebes was formed. The reason for this was the fact that Philip marched together with his army towards Delphi, at request of the central Greek cities as the small city Amphissa would have annexed territory of the holy Delphic oracle. Philip would punish Amphissa, but both Athens and Thebes believed that he had other intentions and formed an army to fight off this new threat. That Demosthenes' political and propagandist efforts almost succeeded is shown by the closeness of Philip's final victory on the field at Chaeronea in 338.

In 337 Philip realised his leadership over the Greek world by inviting all Poleis to a congress at Corinth. The result of this congress was the League of Corinth, whose goal it was to end the endless political conflicts between the cities which ended up in armed conflicts. War between members was forbidden, arbitration was obligatory, and a compromise that was taken in the council of the League had to be collective guaranteed by all members. The autonomy of the members was also guaranteed, which implied that they did not have to pay any taxes or tributes to Macedon and that Macedon had no right to install garrisons in the cities. Nevertheless did Philip place garrisons in three key positions: Thebes, Chalcis and Corinth.