Philip's remaining allies begin to waver but…

The Phocians, now led by Onomarchus, debate whether to make peace, but Onomarchus persuades is countrymen to melt down gold and silver ornaments to make coins to pay another army; and has bronze and iron beaten into new armor and weapons.

Onomarchus now forms an alliance with Lycrophon, the ruler of the Thessalian city of Pherae.

Thessaly as a whole had been willing enough to declare war on Phocis in keeping with an enmity of immemorial antiquity already remarked on as long-standing by Herodotus in the context of the Persian Wars.

Nonetheless, Thessalian unity is limited, as is Theban ability to influence events in Thessaly, and Onomarchus evidently succeeds in exploiting this fluid situation.

In a further complication, …

…another Thessalian city, Larissa, responds by issuing an invitation that is ultimately to be disastrous to Greek, as well as merely to Thessalian, freedom: it calls in Philip.

Onomarchus sends his brother Phayllus with seven thousand troops; but when they are beaten back by the Macedonians, Onomarchus leads twenty thousand men to victory over Philip's forces (his only defeat in the field), which then withdraw from Thessaly.

The victory for Onomarchus' Phocians over Philip, owing (it seems) to overconfidence and failure of reconnaissance, is unexpected; the Phocians seem to have had a “secret weapon,” in the form of nontorsion artillery.

Onomarchus, fielding twenty thousand infantry and less than a thousand cavalry, meanwhile leads his troops south into Boeotia and captures Coronea.

The Thebans, in need of ready cash, hire their citizen-mercenary forces under Pammenes out to Artabazus in his revolt against Persia, but Pammenes is suspected by Artabazus of treachery and imprisoned.

Both Sparta and Arcadia are asking Athens for military assistance against Philip by 353.

Sparta threatens to win back Messenia and …

…the Arcadian city of Megalopolis, which has been weakened by the failure of the Arcadian League and now appeals to Athens for support; but …

…the influential politician Eubulus, backed by the Athenian assembly, does not agree with the anti-Macedonian politician Demosthenes that Athens should interfere.

With Theban help, however, the Messenians, Arcadians, and Argives are able to defend themselves against the Spartans, who are aided by three thousand Phocians, and in 353 foil the Spartan attempt to take Megalopolis.

Philip of Macedon in 353 or 352 BCE leads an army of twenty thousand infantrymen and three thousand cavalry on a lightning march against the port of Pagasae, seizing it before the Athenian fleet, commanded by Chares, can dock and unload their five thousand hoplites and five hundred cavalry.

Philip decks his army in laurel wreaths to signify that they fight on behalf of Apollo against the sacrilegious Phocians.

Leaving a rearguard, he marches against Onomarchus, while the Athenians, absent beaches where they can offload their troops, can only watch the battle from their triremes anchored offshore.

Onomarchus and six thousand Phocian soldiers die in the Battle of the Crocus Field, with more drowning as they attempt to swim to the Athenian ships; three thousand more are captured.

The Phocians appoint Phayllus leader and withdraw southwards, pursued by Philip.

Philip continues to move south, employing bribery and threat as well as military force.

The Athenians in response send a small force to close off the pass at Thermopylae.