Phalacus was the last leader of the Phocians during the Third Sacred War, and survived the defeat of Phocis, only to die during a siege on Crete.
Phalacus was the son of Onomarchus, the second Phocian leader of the war. When his father died after the battle of the Crocus Field (352 BC) Phalacus was perhaps too young to take command, and the power went to his uncle Phayllus. After a brief, and rather unsuccessful, period in command, Phayllus died of natural causes in 351 BC, having named Phalacus as his successor. Because of his youth he was given one of Phayllus's friends, Mnaseas, as a guardian. This arrangement didn’t last for long - Mnaseas was killed in a night battle with the Boeotians, leaving Phalacus in sole command. Phalacus didn’t do much better, losing his first battle in command, a cavalry battle soon after the death of Mnaseas.
For most of his time in command the war was dominated by low level border raids. Diodorus ends up reporting skirmishes in which only seventy were killed or minor raids in which some crops were destroyed.
In 347 BC Phalacus was accused of using part of the sacred treasures for his private benefit, and was removed from power. One of the accusations was that his staff had attempted to dig up the temple of the Oracle, in the belief that there was more treasure buried under the tripod, and only stopped when an earthquake convinced them the gods were angry. According to Diodorus he was replaced by three generals, who discovered that his uncle Phayllus had turned 120 gold bricks donated by Croesus, 360 golden goblets and golden statues of a lion and of a women into coins worth 4,000 silver talents.
In 346 BC he was restored to power, possibly to deal with the increasing threat from Philip II of Macedon. If this was the case, then his appointment was an abject failure. He fell out with his Athenian allies, and behaved so badly towards Archidamus of Sparta that he took his troops home.
While this was going on Philip was moving south to intervene in the war, having entered into negotiations with the Athenians and Thebans. Phalacus badly mishandled the defence of Phocis, allowing Philip to get past Thermopylae without a fight while he waited in the nearby town of Nicaea. He then entered into negotiations with Philip, and was allowed to retire to the Peloponnese with 8,000 mercenaries. It is also possible that he had already made this agreement with Philip, thus explaining his poor performance. With their army gone, the Phocians were forced to agree to Philip's terms, ending the Third Sacred War
For the rest of his life Phalacus worked as a mercenary commander. At first he remained in the Peloponnese, but the money soon ran out. He then decided to take his men west to Italy and Sicily, in the hope that he could either seize a city or gain employment in the war between the Tarentines and the Lucanians. He told his men that they had been summoned by the Tarentines, but after they had put to sea his men became suspicious, as there were no representatives from the Tarentines onboard ship. They mutinied and forced him to return to the Peloponnese.
He then moved to Crete, to fight for the Cnossians against Lyctus. He captured Lyctus, but by an unfortunate chance Archidamus of Sparta was at large with an army that had genuinely been raised to help the Tarentines. Before leaving for Italy he received a call for help from Lyctus, diverted his forces to Crete, defeated Phalacus and then continued on to Italy (where he was killed in battle in 338 BC).
Back on Crete Phalacus moved on to attack Cydonia. Diodorus records two versions of his death. In the first he had built a number of siege engines, but as they were being moved into place they were set on fight by lightning. Phalacus and a number of his men were killed while attempting to save the precious siege engines. In the second he was killed by one his mercenaries. The surviving mercenaries returned to the Peloponnese to help some Eleian exiles, but they were defeated in battle by the Arcadians and the non-exiled Eleians. About 4,000 survivors were captured. Half were sold into slavery by the Arcadians, the others were executed by the victorious Eleians as punishment for their role in the Third Sacred War.