Battle of Mantinea
Deprived of land and its serfs, Sparta declined to a second-rank power. The Theban hegemony thus established was short-lived; at the Battle of Mantinea in 362 BC, Thebes lost its key leader, Epaminondas, and much of its manpower, even though they were victorious in battle. In fact, such were the losses to all the great city-states at Mantinea that none could dominate the aftermath.