But since their misfortune off Actium the Corinthians had been unremittingly assiduous in repairing their loss, and in preparing to revenge it. Triremes were built, all necessaries for a fleet were largely collected, rowers were engaged throughout Peloponnesus, and where else in any part of Greece they could be obtained for hire. The Corcyræans, informed of these measures, notwithstanding their past success were uneasy with the consideration that their commonwealth stood single, while their enemies were members of an extensive confederacy; of which, though a part only had yet been induced to act, more powerful exertions were nevertheless to be apprehended. In this state of things it appeared necessary to abandon their ancient policy, and to seek alliances. Thucydides gives us to understand that they would have preferred the Peloponnesian to the Athenian confederacy; induced, apparently, both by their kindred origin, and their kindred form of government. But they were precluded by the circumstances of the existing war, Corinth being one of the most considerable members of the Peloponnesian confederacy; and it was beyond hope that Lacedæmon could be engaged in measures hostile to so old and useful an ally. It was therefore finally resolved to send an embassy to Athens. As soon as the purpose of the Corcyræans was known at Corinth, ambassadors were sent thence to Athens to remonstrate against it.
The Athenian people were assembled to receive the two embassies, each of which, in presence of the other, made its proposition in a formal oration. The point to be determined was highly critical for Athens. A truce existed, but not a peace, with a confederacy inferior in naval force, but far superior by land; and Attica, a continental territory, was open to attack by land. But next to Athens Corcyra was the most powerful maritime republic; and to prevent the accession of its strength, through alliance, or through conquest, to the Peloponnesian confederacy, was, for the Athenian people, highly important. In the articles of the truce moreover it was expressly stipulated, that any Grecian state, not yet a member of either confederacy, might at pleasure be admitted to either. But, notwithstanding this, it was little less than certain that, in the present circumstances, an alliance with Corcyra must lead to a rupture with the Peloponnesians; and this consideration occasioned much suspense in the minds of the Athenians. Twice the assembly was held to debate the question. On the first day, the arguments of the Corinthian ambassadors had so far effect that nothing was decided: on the second, the spirit of ambition, ordinary in democracy, prevailed, and the question was carried for alliance with Corcyra.
[433 B.C.]
Meanwhile the earnestness with which the Corinthians persevered in their purpose of prosecuting war against the Corcyræans, now to be supported by the power of Athens, appears to mark confidence in support, on their side, from the Lacedæmonian confederacy; some members of which indeed were evidently of ready zeal. The Corinthians increased their own trireme galleys to ninety. The Eleans, resenting the burning of Cyllene, had exerted themselves in naval preparation, and sent ten triremes completely manned to join them. Assistance from Megara, Leucas, and Ambracia made their whole fleet a hundred and fifty: the crews would hardly be less than forty thousand men. With this large force they sailed to Chimerium, a port of Thesprotia, over against Corcyra, where, according to the practice of the Greeks, they formed their naval camp.
The Athenian government meanwhile, desirous to confirm their new alliance, yet still anxious to avoid a rupture with the Peloponnesian confederacy, had sent ten triremes to Corcyra, under the command of Lacedæmonius, son of Cimon; but with orders not to fight, unless a descent were made on the island, or any of its towns were attacked. The Corcyræans, on receiving intelligence that the enemy was approaching, put to sea with a hundred and ten triremes, exclusive of the Athenian, and formed their naval camp on one of the small islets called Sybota, the Sow-leas or Sow-pastures, between their own island and the main. Their land-forces at the same time, with a thousand auxiliaries from Zacynthus, encamped on the headland of Leucimme in Corcyra, to be prepared against invasion; while on the opposite coast of the continent the barbarians, long since friendly to Corinth, assembled in large number. The Corinthians however, moving in the night, perceived in the dawn the Corcyræan fleet approaching. Both prepared immediately to engage.