Again the Thebans refused to renounce their Boeotian hegemony, and the Spartan attempt at coercion ended in the defeat of the Spartan army at the battle of Leuctra and the death of its leader, King Cleombrotus.
The city was reconstituted after the battle of Leuctra and under its statesman Lycomedes played a prominent part in organizing the Arcadian League (370).
After the battle of Leuctra Argos experienced a political crisis; the oligarchs attempted a revolution, but were put down by their opponents with such vindictiveness that 1200 of them are said to have been executed (370).
The worst trait in his character is his implacable hatred of Thebes, which led directly to the battle of Leuctra and Sparta's fall from her position of supremacy.
After the battle of Leuctra the philo-Laconian party was expelled with Mantineian help. Tegea henceforth took an active part in the revival of the Arcadian League and the prosecution of the war in alliance with Thebes against Sparta (371-362), and the ultimate defection of Mantineia confirmed it in its federalist tendencies.
After the battle of Leuctra (371 B.C.) Epaminondas invited the exiled Messenians scattered in Italy, Sicily, Africa and elsewhere to return to their country: the city of Messene was founded in 369 to be the capital of the country and, like Megalopolis in Arcadia, a powerful check on Sparta.