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
Beyond Diodorus, further details of the Sacred War can be found in the orations of Athenian statesmen, primarily Demosthenes and Aeschines, which have survived intact. Since these speeches were never intended to be historical material, they must be treated with circumspection; Demosthenes and Aeschines have been described as "a couple of liars, neither of whom can be trusted to have told the truth in any matter in which it was remotely in his interest to lie". Nevertheless, their allusions in speeches to contemporary or past events indicate some of the gaps in Diodorus's account, and help with the arrangement of a chronology. The accounts of Diodorus, Demosthenes and Aeschines can be further supplemented by fragments of otherwise lost histories (such as that by Theopompus) and by contemporary epigraphic sources.