Expansion of Macedonia under Philip II
The Third Sacred War (often just called 'the' Sacred War) broke out in 356 BC, and would present Philip with his first real opportunity to expand his influence into the affairs of central and southern Greece. The war was ostensibly caused by the refusal of the Phocian Confederation to pay a fine imposed on them in 357 BC by the Amphictyonic League, a pan-Greek religious organisation which governed the most sacred site in Ancient Greece, the Temple of Apollo at Delphi. Behind the religious element, there probably lay a display of "realpolitik" in bringing charges against the Phocians, instigated by the Thebans. At this time, Thebes controlled a majority of the votes in the council, and at the autumn meeting in 357 BC, the Thebans were able to have both the Phocians (for the cultivation of the sacred land) and the Spartans (for occupying Thebes some 25 years previously) denounced and fined. Since the fines for both parties were "unjustifiably harsh", the Thebans probably expected neither party to pay, and thus to be able to declare a "sacred war" on either.
Battle of Chaeronea (338 BC)
Philip was not originally a belligerent in the Sacred War, but became involved at the request of the Thessalians. Seeing an opportunity to expand his influence into Greece proper, Philip obliged, and in 353 or 352 BC won a decisive victory over the Phocians at the Battle of Crocus Field in Thessaly. In the aftermath, Philip was made "archon" of Thessaly, which gave him control of the levies and revenues of the Thessalian Confederation, thereby greatly increasing his power. However, Philip did not intervene further in the Sacred War until 346 BC. Early in that year, the Thebans, who had borne the brunt of the Sacred War, together with the Thessalians, asked Philip to assume the "leadership of Greece" and join them in fighting the Phocians. Philip's power was by now so great that ultimately the Phocians did not even attempt to resist, and instead surrendered to him; Philip was thus able to end a particularly bloody war without any further fighting. Philip allowed the Amphictyonic council the formal responsibility of punishing the Phocians, but ensured that the terms were not overly harsh; nevertheless, the Phocians were expelled from the Amphictyonic League, all their cities were destroyed, and they were resettled in villages of no more than fifty houses.