Battle of Mantinea

In this battle it was primarily a question of who would be the leading force in Greece, Sparta or Thebes. The first army of the Thebans, the Arcadian Commonwealth and the Boeotians was led by Epameinondemos, while the second warring party of Spartans, Athenians, Elidians and Mantineans was led by King Agesilaus II.

After the Battle of Leukter (371 BC), the dominance of Sparta was weakened and the Theban politician and warlord Epameinóndás attempted to establish the hegemony of Thebes. He therefore decided to invade the Peloponnese with the support of the Arcadian League and the Boeotians. The Eleans joined Sparta because of their mutual hostility with the Arcadians. And Athens, because they disliked the Theban expansionism, and also because after the Peloponnesian War the Thebans demanded the destruction of Athens and the enslavement of its inhabitants.

The two armies clashed near Mantinea. Epameinóndás used improved tactics to win, as he had already done at the Battle of Leukter. Namely, the phalanx formation (a close-quartered rectangular formation of infantry, usually hoplites or lancers, that dominated European battlefields for much of antiquity and the Middle Ages), which he modified by deploying the Boeotian troops on the left flank of his army in an unusually deep mass of hoplites. Thus reinforced, he led the left flank himself and drove the best Spartan troops into retreat. In the fight, however, he himself suffered mortal wounds, and so did his eventual deputies Iolaidas and Daifantos. Before his death, he issued instructions to make peace despite the Theban victory.

Without a strong leader, Thebes greatly weakened its influence, but even Sparta could not manage the position of the strongest state. The war resulted in the weakening of both sides and the gradual rise of King Philip II of Macedonia.