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
Philip thus brought an army into Thessaly, probably with the intention of attacking Pherae. Under the terms of their alliance, Lycophron of Pherae requested aid from the Phocians, and Onormarchos dispatched his brother, Phayllos with 7,000 men; however, Philip repulsed this force before it could join up with the Pheraeans. Onomarchos then abandoned the siege he was currently prosecuting, and brought his whole force into Thessaly to attack Philip. It is possible that Onomarchos hoped to conquer Thessaly in the process, which would both leave the Thebans isolated (Locris and Doris having already fallen to the Phocians), and give the Phocians a majority in the Amphictyonic council, thus enabling them to have the war declared over. Onomarchos probably brought with him 20,000 infantry, 500 cavalry, and a large number of catapults, and outnumbered Philip's army. The exact details of the campaign that followed are unclear, but Onomarchos seems to have inflicted two defeats on Philip, with many Macedonians killed in the process. Polyaenus suggests that the first of Onomarchos's victories was aided by the use of the catapults to throw stones into the Macedonian phalanx, as they climbed a slope to attack the Phocians. After these defeats, Philip retreated to Macedon for the winter. He is said to have commented that he "did not run away but, like a ram, I pulled back to butt again harder".