The Boeotian League intervenes also in the Arcadian federation in the Peloponnese, which has split in two; the Tegean party appeals for help to the Thebans (who in turn have for allies the Argives and Messenians), and …

…the Mantineans to Athens and Sparta.

The outbreak of civil war in the Arcadian league in 362 brings Epaminondas once more to the head of a large allied army in the Peloponnese.

Leading the Boeotians and their Argive allies against Sparta, Athens, and their allies in an encounter on the Mantineian Plain, Epaminondas repeats on a large scale the tactics of Leuctra, cleverly outmaneuvering the Spartan troops, and is once more victorious but dies of a wound on the field of battle.

The great Battle of Mantinea (“Second Mantinea,” to distinguish it from the events of 418) is a technical victory for Thebes in the strictly military sense, but (as Xenophon notes) it is actually indecisive: Epaminondas' death permanently crushes Theban hopes of leadership in Greece.

The peace after the battle in effect recognizes the independence of the Messenians, thus settling at the diplomatic level an issue that in reality has been settled for years.

All constructive initiative appears to vanish with the death of Epaminondas from the policy of Thebes, which begins a rapid decline from its decade-long position as Greece's preeminent city-state.