The battle of the Crocus Field or of Pagasae (353 BC) was a significant victory for Philip II of Macedon and saw him defeat and kill Onomarchus, the Phocian leader, a victory that helped to secure Philip's dominance over Thessaly.
At first Philip hadn't been affected by the Third Sacred War, which saw the Phocians defy a judgement against them, occupy the Oracle at Delphi, and inflict a number of defeats on their Locrian, Thessalian and Boeotian enemies. The two sides eventually came into conflict as a result of events in Thessaly. In 354 BC Philip responded to a call for help from his Thessalian allies, who were threatened by Lycophron, tyrant of Pherae. Lycophron responded to this threat by asking for help from the Phocians. Onomarchus, the Phocian leader, sent an army commanded by his brother Phayllus into Thessaly, but Philip quickly defeated this army. Onomarchus then led the main Phocian army into Thessaly in person, and inflicted two rare defeats on Philip.
In the aftermath of these defeats Philip returned to Macedon to regroup, while Onomarchus moved into Boeotia, where he defeated the Boeotians at the battle of Hermeum, and captured Coronea.
Philip didn't take long to recover from his defeats. In 353 BC he led his army back into Thessaly, where he attacked the port at Pagasae. He was joined by his Thessalian allies, producing an army that Diodorus reports as containing 20,000 infantry and 3,000 cavalry (Diodorus 16.35.4). Lycophron sent desperate messages to Phocis asking for help and promising to share the government of Thessaly. Onomarchus led his army north, bringing 20,000 infantry and 500 cavalry of his own. He was probably also hoping for Athenian help (in a list of Athenian failures Demosthenes includes their failure to provide aid to Pagasae in time).
The resulting battle took place on a large plain near the sea, probably the area known as the Crocus Field. According to Diodorus Philip's Thessalian cavalry won the day. Onomarchus fled towards the coast, where an Athenian fleet under Chares was just off shore. In an attempt to reach the safety of the fleet many of the Phocian survivors stripped off their armour and attempted to swim out to the ships. Many of them were killed during this phase of the battle. The Phocians lost 6,000 dead in the battle, while another 3,000 were taken capture and then thrown into the sea as a punishment for robbing the temples at Delphi. Diodorus gives contradictory accounts of the death of Onomarchus. In the main account of the battle (16.35.6) he was crucified by Philip. Later on, when summarising the fates of those involved in the war (16.61.2) he reports that Onomarchus was 'cut to pieces' in a battle in Thessaly and then crucified.
Pausanius gives a different account of Onomarchus's death (10.2.5). In his account Onomarchus was shot down by his own troops while fleeing to the coast, as they blamed him for the defeat.
Once again the Phocians managed to recover from a potentially crushing defeat. Onomarchus was replaced by his brother Phayllus, and then by Onomarchus's son Phalacus, and the war dragged on until 346. Philip may have intended to invade Phocis in the aftermath of the battle, but he delayed his move south too long, and the worried Athenians were able to block the pass at Thermopylae. Philip didn’t want to risk a defeat, and returned home.