The naval Battle of Pylos took place in 425 BC during the Peloponnesian War at the peninsula of Pylos, on the present-day Bay of Navarino in Messenia, and was an Athenian victory over Sparta. An Athenian fleet had been driven ashore at Pylos by a storm, and, at the instigation of Demosthenes, the Athenian soldiers fortified the peninsula, and a small force was left there when the fleet departed again. The establishment of an Athenian garrison in Spartan territory frightened the Spartan leadership, and the Spartan army, which had been ravaging Attica under the command of Agis, ended their expedition (the expedition only lasted 15 days) and marched home, while the Spartan fleet at Corcyra sailed to Pylos.
Demosthenes had five triremes and their complements of soldiers as a garrison, and was reinforced by 40 hoplites from a Messenian ship that happened to stop at Pylos. In total, Demosthenes probably had about 600 men, only 90 of which were hoplites. He sent two of his triremes to intercept the Athenian fleet and inform Sophocles and Eurymedon of his danger. The Spartans, meanwhile, had 43 triremes and a large land army. Finding himself thus outnumbered, Demosthenes pulled his remaining three triremes up on land and armed their crews with whatever weapons were at hand. He placed the largest part of his force at the strongly fortified point facing the land. Demosthenes then hand-picked 60 hoplites and a few archers and brought them to the point where he anticipated the Spartans would launch their amphibious assault. Demosthenes expected that the Spartans would hit the south-west corner of the peninsula where the defensive wall was the weakest and the land was most suitable for a landing. The Spartans attacked where Demosthenes had expected, and the Athenians were faced with simultaneous assaults from land and sea. The Athenians held off the Spartans for a day and a half, however, causing the Spartans to cease their attempts to storm Pylos and instead settled in for a siege.