History of the Peloponnesian War

It was now late and the paean had been sounded for the onset, when the Corinthians suddenly began to back water; for they sighted twenty Attic ships approaching, which the Athenians had sent out after the ten as a reinforcement, fearing just what happened, namely that the Corcyraeans would be defeated and their own ten ships would be too few to help them.

So when the Corinthians sighted these ships before the Corcyraeans did, suspecting that they were from Athens and that there were more of them than they saw, they began to withdraw.

For the Corcyraeans, however, the Athenian ships were sailing up more out of view and could not be seen by them, and so they wondered that the Corinthians were backing water, until some of them caught sight of the ships and said, " Yonder are ships sailing up."