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
Modern historians' dates for the war have 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 few firm dates), which yields a date of 356 BC for the beginning of the war, with Philomelos's seizure of Delphi. 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.