[1] Cnemus' earliest recorded military operation during the Archidamian War occurred in the summer of 430 BC, at the island of Zacynthus.
Two of Sparta's allies, the Ambraciots and Chaonians, had convinced the Spartans to invade Acarnania with the purpose of eventually capturing the islands of Cephallenia and Zacynthus.
[4] As the Ambraciots and Chaonians argued, if the campaign succeeded, the Spartans would gain strategic positions, thus enabling them to complicate the Athenians' navigation around the Peloponnesus.
[4] As a result of these urgings, the Spartans decided to send a land force, led by Cnemus, to the Ambracian Gulf to prepare for the invasion of Acarnania.
[6] Cnemus’ plan was that the three divisions would encamp outside Stratus and would regroup to attack the city's walls if negotiations with the Stratians failed.
[8] Not having expected to engage in a sea battle, the Spartan fleet consisted primarily of ships suited only for transporting troops rather than for fighting.
[10] Upon receiving news of the failure of the Acarnanian Campaign, the Spartans became greatly dissatisfied with Cnemus’ command of the fleet.
[11] As a result, three commissioners, Timocrates, Brasidas and Lycophron, were sent by the Spartans to make up for what they perceived as Cnemus’ lack of energy and to help him reorganize the fleet.
[14] Phormio, with the same twenty ships from his victory at Naupactus, set anchor at Molycrian Rhium, directly across the Spartans at the mouth of the Crisaean Gulf.
[18] Ten of the Athenian ships made it to the shore of Naupactus and positioned themselves so as to repel an attack, should the Spartans pursue them further.
[18] The Spartans quickly halted their pursuit and, as a consequence of their lack of familiarity with the local geography, ran several of their ships aground.
[19] After arriving in Corinth, Cnemus and Brasidas allowed the Megarians to convince them to launch an attack on Athens’ port, the Piraeus.
[17] Therefore, although it is not explicitly known why Cnemus and Brasidas agreed to the Megarian plan, some scholars have speculated that neither man was eager to return to Sparta without having gained at least one victory.
[13] Crossing from Corinth to Megara, the Spartans planned to launch forty ships and take the Athenians by surprise.
[24] The following day, the Athenians mustered a ground force to bolster the defences of the Piraeus and launched their fleet to defend Salamis.
[26] In Thucydides' characterization, Cnemus' similarities to the later Spartan fleet commander, Alcidas, may have been exaggerated to contrast and emphasize the superior leadership of the heterodox Brasidas.