OLYNTHUS was an important city of Chalcidice (see vol. XV. p. 137), situated in a fertile plain at the head of the Toronaic gulf between the peninsulas of Sithonia and Pallene, at some little distance from the sea, and about 60 stadia from Potidaea. The district belonged originally to a Thracian people, the Bottiaei; and it is said that it was given over to the Greek colonists of Chalcidice at the Persian invasion. It fell under Athenian influence during the 5th century, but regained its freedom during the invasion of Brasidas (424 b.c. ). It became the head of a great confederacy, and its power excited the jealousy of Sparta. A war broke out 383-379, and Olynthus was compelled to become a member of the Spartan confederacy. No long time afterwards the Athenians made themselves masters of several towns which had previously been under the influence of Olynthus, and then a new and more dangerous enemy appeared on the northern frontier. Philip of Macedon found the city his most powerful rival, and directed all his strength against it. The Athenians made an alliance with Olynthus, but did not give any active aid, though Demosthenes tried hard to induce them to oppose Philip before he grew too strong. The famous series of Olynthiae orations was delivered by him at this crisis. After a long siege the city was captured by treachery in 347 B.c.; it was razed to the ground, and the people sold as slaves.