Third Sacred War
Philip's involvement in the Third Sacred War (356–346 BC) began in 354 BC. At the request of the Thessalian League, Philip and his army traveled to Thessaly in order to capture Pagasae, resulting in an alliance with Thebes. A year later in 353 BC, Philip was once again asked to assist in battle, but this time against the tyrant Lycophron who was supported by Onomarchus. Philip and his forces invaded Thessaly, defeating 7,000 Phocians and forcing Phayllus, the brother of Onomarchus, to leave.
That same year, Onomarchus and his army defeated Philip in two succeeding battles. Philip returned to Thessaly the next summer, this time with an army of 20,000 infantry, 3,000 cavalry, and the additional support of the Thessalian League's forces. At the Battle of Crocus Field, 6,000 Phocians fell and 3,000 were taken as prisoners and later drowned. This battle earned Philip immense prestige as well as the free acquisition of Pherae. He was made the leader (archon) of the Thessalian League and was able to claim Magnesia and Perrhaebia, which expanded his territory to Pagasae. Philip did not attempt to advance into Central Greece because the Athenians, unable to arrive in time to defend Pagasae, had occupied Thermopylae.
There were no hostilities with Athens yet, but Athens was threatened by the Macedonians. From 352 to 346 BC, Philip did not again travel south. He was active in completing the subjugation of the Balkan hill-country to the west and north, and in reducing the Greek cities of the coast as far as the Hebrus. To the chief of these coastal cities, Olynthus, Philip continued to profess friendship until its neighboring cities were in his hands.
In 348 BC, Philip started the siege of Olynthus, which, apart from its strategic position, housed his half-brothers, Arrhidaeus and Menelaus, pretenders to the Macedonian throne. Olynthus had at first allied itself with Philip, but later shifted its allegiance to Athens. The latter, however, did nothing to help the city because its expeditions were held back by a revolt in Euboea. The Macedonian king took Olynthus in 348 BC and razed the city to the ground. The same fate was inflicted on other cities of the Chalcidian peninsula, resulting in the Chalcidian League dissolving.
Macedon and the regions adjoining it having now been securely consolidated, Philip celebrated his Olympic Games at Dium. In 347 BC, Philip advanced to the conquest of the eastern districts about Hebrus, and compelled the submission of the Thracian prince Cersobleptes. In 346 BC, he intervened effectively in the war between Thebes and the Phocians, but his wars with Athens continued intermittently. However, Athens had made overtures for peace, and when Philip again moved south, peace was sworn in Thessaly.
