The siege of Potidaea in 356 saw Philip II of
Macedon capture the strongly fortified city at the head of the Pallene
peninsula, but then hand it over to Olynthus in order to secure an alliance
with that city. Potidaea was located at the narrow neck of the Pallene
peninsula, the westernmost of the three peninsulas of Chalcidice. She had been
a member of the Chalcidian League, led by nearby Olynthus, but in around
363-361 Athens took control of the city.
At the start of his reign Philip II of Macedon had formed an alliance with
Athens, but this was ended by his successful capture of
Amphipolis in 357. This city, to the
east of Chalcidice, had been founded by Athens, but quickly lost to Sparta.
Regaining control of Amphipolis had been a long term Athenian objective, and
after the Macedonians took the city the Athenians declared war, starting the
ten year long 'War of Amphipolis'.
At this point Athens was distracted by the
Social War, a conflict
with her own allies, and was unable to intervene effectively in the north.
Having alienated the Athenians, Philip decided to form an alliance with the
Chalcidian League. At this point the league was in negotiations with the
Illyrian King Grabus, and the Olynthians had also attempted to negotiate an
alliance with Athens. They were rebuffed by the Athenians.
Philip took advantage of this by making them a generous offer. He would hand
over the border territory of Anthemus, and help the Olynthians capture
Potidaea. In return the Olynthians agreed not to enter into an alliance with
Athens without Philip. The siege began around July 356, just as the Etesian
Wind began to blow. This northerly wind made it harder for Athens to send any
fleets into the northern Aegean, so reduced the chance of any interference in
the siege. It is possible that Athens did indeed try and send aid, but if so it
arrived too late. Potidaea surrendered to Philip in the autumn of 356. Any
Athenians found in the city were sent home, but the Potidaeans themselves were
sold into slavery. The city and the surrounding area were then handed over to
Olynthus and the Chalcidic League.
Plutarch records that Philip received three items of good news just after the
fall of the city - the victory of his horse at the Olympics, Parmenion's
victory over Grabus and the birth of the future Alexander the Great. This story
doesnt entirely work, as Alexander is said to have been born in July 356
and the Olympics were held in August or September, but it does demonstrate how
much progress Philip had made in the first few months of his reign. Olynthus
didnt enjoy its success for too long. Their relationship with Philip soon
soured, and the city was besieged and destroyed in 348.