Thucydides, History of the Peloponnesian War
Benjamin Jowett, Ed.

10. Meanwhile the Isthmian games were celebrated. The Athenians, to whom they had been¹ formally notified, sent representatives to them; and now their eyes began to be opened to the designs of the Chians. On their return home they took immediate measures to prevent the enemy's ships getting away from Cenchreae unperceived. [2] When the games were over, the Peloponnesians, under the command of Alcamenes, with their twenty-one ships set sail for Chios; the Athenians, with an equal number, first sailed up to them and tried to draw them into the open sea. The Peloponnesians did not follow them far, but soon turned back to Cenchreae; the Athenians likewise retired, because they could not depend on the fidelity of the seven Chian ships which formed a part of their fleet. [3] So they manned some more ships, making the whole number thirty-seven, and when the Peloponnesians resumed their voyage along the coast they pursued them into Piraeum, a lonely harbour, the last in the Corinthian territory before you reach Epidauria. One ship was lost by the Peloponnesians at sea, but they got the rest together and came to anchor in the harbour. [4] Again the Athenians attacked them, not only on the water, but also after they had landed; there was a fierce struggle, but no regular engagement; most of the enemy's ships were damaged by the Athenians on the beach, and their commander, Alcamenes, was slain. Some Athenians also fell.