Battle of Leuctra
After the defeat of the Spartan army at the Battle of Leuctra in Boeotia, 371 BC, the helots of Messenia revolted yet again against their Spartan overlords. This time the victorious general, Epaminondas, entered the Peloponnesus with an army of Boeotians, Argives and Messenians living abroad. Epaminondas resolved to support an independent Peloponnesus by building three fortified cities, Megalopolis and Mantinea in Arcadia and Messene in Messenia.