The History of the Grecian War (1.31.1-1.31.3)

All this year, as well before as after the battle, the Corinthians, being vexed at the war with the Corcyraeans, applied themselves to the building of galleys and to the preparing of a fleet, the strongest they were able to make, and to procure mariners out of Peloponnesus and all other parts of Greece.

The Corcyraeans, having intelligence of their preparations, began to fear and (because they had never been in league with any Grecian city, nor were in the roll of the confederates either of the Athenians or Lacedaemonians) thought it best now to send to Athens to see if they could procure any aid from thence.

This being perceived by the Corinthians, they also sent their ambassadors to Athens, lest the addition of the Athenian navy to that of the Corcyraeans might hinder them from carrying the war as they desired.