The first event in this period was the battle of Leuctra (July 371), in which, no doubt to the surprise of Athens, Thebes temporarily asserted itself as the chief land power in Greece.
Since 387 the Spartan party was again supreme, and after Leuctra Corinth took the field against the Theban invaders of Peloponnesus (371-366).
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, when the power of Thebes was founded by Epaminondas, Pelopidas went to Susa (367) and restored the old alliance between Persia and Thebes.
The city was reconstituted after the battle of Leuctra and under its statesman Lycomedes played a prominent part in organizing the Arcadian League (370).