Battle of Crocus Field
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 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
All of central and southern Greece was now at Philip's mercy, and the Athenians could not now save Phocis even if they abandoned the peace. However, the Athenians were still ignorant of this turn of events when Phocian ambassadors came to Athens to plead for military aid around 9 July. The Athenian council recommended that the peace be rejected, and Thermopylae be occupied in order to help save Phocis; since, as far at the Athenian embassy knew, Philip's troops were still in Pherae, there seemed to be ample time to occupy the pass. By 12 July the news that Philip was "in the gates" arrived in Athens; the Athenians then knew that the situation was hopeless, and instead of acting on the previous recommendation of the council, the Assembly instead passed a motion re-affirming the Peace of Philocrates.