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
The destruction of the Phocian cities and the heavy fine imposed on the Phocian confederation certainly caused the Phocians to bear a grudge against Philip II. Seven years later the Locrians brought charges against the Athenians in the amphictyonic council and a special session of the council was set in order to deal with that matter. The Athenians, however, did not send envoys and neither did the Thebans. This was a clear insult to the council and Philip II intervened once more as a regulator. The Fourth Sacred War broke out, ending in the total subjugation of Greece to the kingdom of Macedonia. The Phocians recovered gradually from the repercussions of the Third Sacred War and managed to be reinstated in the Amphictyony in 279 BC, when they joined forces with the Aetolian League fighting against the Gauls. 
However, a serious side-loss of the Third Sacred War remained the destruction of a large number of ex votos and other precious offerings to the sanctuary of Apollo, which deprived not only the sanctuary itself but also the later generations of some magnificent pieces of art.