The Battle of Mantinea was a major battle of the Peloponnesian War which was fought in Arcadia in 418 BC.
The conclusion of the 421 BC "Peace of Nicias" between the Spartan-led Peloponnesian League and the Athenian-led Delian League failed to bring an end to the fighting in Greece, as skirmishes continued in and around the Peloponnese, and, due to Sparta's inaction, some of Sparta's allies considered a revolt. With the support of Athens, the independent city-state of Argos formed a coalition of democratic allies in the Peloponnese, including Mantinea and Elis, to counter Sparta's growing power. An Argive and Athenian army under Alcibiades promptly moved to seize the Spartan-allied Arcadian city of Tegea, resulting in a Spartan and Tegean army facing an alliance of Argos, Athens, Mantinea, and Arcadia at Mantinea. The Spartan army consisted of 3,000 Arcadian allies, 900 of Brasidas' veterans, 600 Sciritae (elite skirmishers), and 2,000 neodamodes (freed helots). In the ensuing battle, the Argives took advantage of a gap in the Spartan line to charge in and rout the Brasidians and the Sciritae, but the Spartan regulars routed the Argive and Arcadian center. The Athenians who formed the left were then encircled, and only an attack by their cavalry spared them from destruction. Agis proceeded to support his hard-pressed left, routing the Mantineans with heavy losses, while the elite "Argive Thousand" escaped virtually unharmed. The Spartans did not pursue the enemy for long, and, after the battle, Argos agreed to a truce and ceded Orchomenus and aided Sparta in evicting the Athenians from Epidaurus. The Argives also renounced their alliance with Elis and Athens, and the Argive Thousand overthrew Argos' democratic government in a coup.