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.
Third Sacred War
When Philip returned from Thrace he received both the Athenian and other embassies. The Thebans and Thessalians requested that he take the leadership of Greece, and punish Phocis; conversely, the Phocians, supported by the Spartans and the Athenian delegations, pleaded with Philip not to attack Phocis. Philip, however, delayed making any decisions; "[he] sought by every means not to reveal how he intended to settle things; both sides were privately encouraged to hope that he would do as they wanted, but both were bidden not to prepare for war; a peacefully arranged concordat was at hand"; he also delayed taking the oaths to the Peace of Philocrates. Military preparations were ongoing in Pella during this period, but Philip told the ambassadors that they were for a campaign against Halus, a small Thessalian city which held out against him. He departed for Halus before making any pronouncements, compelling the Athenian embassy to travel with him; only when they reached Pherae did Philip finally take the oaths, enabling the Athenian ambassadors to return home.