During the Peloponnesian War (431–404 BCE) Nafpaktos was the main Athenian naval base in western Greece. The city was populated with Messenians, who had lost their homeland to the Spartans and were therefore both fierce enemies of Sparta and friendly towards Athens (that lead the war against Sparta). Nafpaktos had a good harbour and its location enabled the Athenians to control the movement of the Corinthian navy, the main naval force that could wrestle control of the seas from Athens. In the summer of 429 BCE Sparta decided it was time to attack Nafpaktos and sent a large force of 47 ships to defeat an Athenian fleet of 20 triremes.