The battle of Chaeroneia (c.352 BC) was an early defeat in the career of Phalacus as leader of the Phocians (Third Sacred War).
In 353 the successful Phocian commander Onomarchus was killed at the battle of the Crocus Field in Thessaly, a major Phocian defeat at the hands of Philip II of Macedon. He was succeeded by his brother Phayllus, who proved to be a rather unsuccessful commander. He did manage to create a fresh army to replace the one last at the Crocus Field, but then led it to a series of defeats in Boeotia (Orchomenus, the Cephisus River and Coroneia) and at Abae, on the borders of Phocis. During this period Phayllus was suffering from a wasting disease, and soon after the defeat at Abae he died.
After the death of Phayllus he was succeeded as general by Phalacus, the young son of his brother Onomarchus. Phayllus had had time to make proper preparations for the succession, and appointed his friend Mnaseas as Phalacus's guardian.
This arrangement didn't last for long. Mnaseas and two hundred of his men were killed when the Boeotians carried out a night attack on his camp. This left Phalacus without his guardian, and he was further undermined when he suffered a defeat in a cavalry battle near Chaeroneia. Diodorus gives little detail of the battle, other than to say that Phalacus lost a 'large number' of cavalry (Diodorus 16.38.7).
Phalacus wasn't discouraged by this defeat. Possibly later in the same year the Boeotians were distracted by a conflict in the Peloponnese, and Phalacus took advantage of this to occupy Chaeroneia. This was a short-lived success, and he was forced to retreat when the main Boeotian army returned. This was followed by a Boeotian invasion of Phocis, but the Boeotian army retired after gathering a great deal of loot.
This ended a rather eventful year, but one that had failed to bring any end to the conflict. The war dragged on for several more years, and didn't end until 346 BC, but for most of the time it was limited to skirmishes close to the border between Phocis and Boeotia.