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.
Expansion of Macedonia under Philip II
The ancient sources for the sacred war are scant, and generally lacking in firm chronological information. Modern historians' dates for the war have therefore been hotly debated, with no clear consensus. It is generally accepted that the war lasted 10 years, and ended in summer 346 BC (one of the only firm dates), which yields a date of 356 BC for the beginning of the war, with Philomelos's seizure of Delphi. After Philomelos's defeat at Neon, the Thebans thought it safe to send the general Pammenes to Asia with 5000 hoplites; as has been discussed, Pammenes probably met with Philip at Maroneia in 355 BC, presumably on his outward journey. Buckler, the only historian to produce a systematic study of the sacred war, therefore places Neon in 355 BC, and suggests after the meeting with Pammenes, Philip went to begin the siege of Methone. Other historians have placed Neon in 354 BC, because Diodorus says that the battle took place while Philip besieged Methone which Diodorus (at one point) places in 354 BC. However, Diodorus's chronology for the sacred war is very confused—he dates the start and end of the war a year too late, variously says the war lasted 9, 10 or 11 years, and included the siege of Methone twice under different dates—and his dates cannot therefore be relied upon.