It was probably in the spring of 382 that Teleutias, brother of Agesilaus, marched against the city with a large army. He had made up the number of his forces in Thebes, and had received auxiliary contingents from Amyntas and from Derdas, prince of Elimea. This was the beginning of a fierce and prolonged struggle. After some successes which allowed him to press forward to Olynthus itself, devastating the country as he went, he fell in a hotly contested battle, and his death was the signal for a general flight. His whole army was swept away and annihilated. With amazing perseverance the Spartans continued the war; in the spring of 380 another huge army was equipped and the leadership entrusted to the young king, Agesipolis. He was fortunate in battle, but succumbed to a violent fever the same summer. It was left for Polybiades, his successor in the command, to force the starving city, cut off from access to the sea and robbed of its harvests by the prolonged and desolating war, into surrender. In the year 379 the league was dissolved and the proud city compelled to render military service to the Spartans; the mighty chief city of the Chalcidice became a humble member of the Lacedæmonian alliance.
[380-379 B.C.]
Meanwhile the Peloponnesus itself had become the scene of a fresh struggle. It has already been mentioned that the exiled aristocrats from Phlius had been allowed to return at the request of Sparta and had been promised the restoration of their property. But here, as everywhere, the attempts at expropriation met with almost insurmountable obstacles. There may have been a lack of good will to push on the proceedings, since it is probable that in many cases the judges themselves were in possession of the estates of the exiles. But in the beginning, at least, there seems to have been no excessive difficulty or delay in giving compensation, and we hear that, in the campaign of Agesipolis, the Phliasians distinguished themselves as zealous allies of Sparta by the liberality and promptitude of their contributions. After the departure of Agesipolis, as Xenophon relates, the Phliasians hoping to be quit of Spartan intervention, neglected the settlement of the chaotic claims. The returning aristocrats, finding their demands disregarded by an unbiassed court of arbitration, turned with their grievances to Sparta. The authorities of their own city having punished them for this arbitrary proceeding, the ephors, persuaded by exiles and by Agesilaus, the fast friend of the latter, determined upon a campaign against Phlius. The Phliasians sued for peace, but naturally could not accede to the demand of Agesilaus for an unconditional surrender of their citadel.
A tedious siege then began, during which Agesilaus found himself obliged to have recourse to every kind of artifice to allay the wrath of the Lacedæmonians and their allies at making enemies of the large population of the Asopus valley for the sake of a few oligarchs. It was the first note of that discord among the Peloponnesian allies which was destined to exercise such a paralysing effect upon the future military undertakings of the Lacedæmonians. Thanks to the valiant defence of Delphion, to whom Xenophon does not refuse his due meed of praise, the city held out twice as long as had been expected. At last, in the year 379, the lack of provisions constrained the inhabitants to treat for peace, and, unwisely ignoring Agesilaus, they applied direct to Sparta. Sparta committed the sole decision to the king, and the punishment in store for Phlius was naturally not the less severe for the attempt to set Agesilaus aside. A commission was appointed, consisting of fifty oligarchs and fifty of the citizens, and they were empowered to decide the question which of the inhabitants should remain alive and which should not. The further duty of elaborating a constitution was also assigned to them. To safeguard the new order of things a Lacedæmonian garrison was left provisionally in the acropolis. Thus in Phlius, as in Olynthus, Sparta had won the victory.