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
Following the declaration of war against Phocis, Philomelos decided he would need to substantially increase the size of his army. Rather than levy the Phocian citizen body, Philomelos decided to hire more mercenaries; the only way he could afford to do this was by plundering the dedications in the treasury of Apollo. That the treasury contained much wealth, from years of accumulated donations, is well-established; it is estimated that the Phocians spent some 10,000 talents of Apollo's treasure during the war. In order to overcome the reluctance of mercenaries to fight for a sacrilegious cause, Philomelos increased the rate of pay by half, which allowed him to recruit a force of 10,000 troops over the winter, for the forthcoming war.