History of the Peloponnesian War

About the end of the same winter Salaethus, a Lacedaemonian, was sent in a galley to Mytilene and, coming first to Pyrrha and thence going to Mytilene by land, entered the city by the dry channel of a certain torrent, which had a passage through the wall of the Athenians, undiscovered. And he told the magistrates that Attica should again be invaded and that the forty galleys which were to aid them were coming, and that himself was sent afore both to let them know it and withal to give order in the rest of their affairs.

Hereupon the Mytilenaeans grew confident and hearkened less to composition with the Athenians. And the winter ended, and the fourth year of this war written by Thucydides.

In the beginning of the summer after they had sent Alcidas away with the forty-two galleys, whereof he was admiral, unto Mytilene, both they and their confederates invaded Attica to the end that the Athenians, troubled on both sides, might the less send supply against the fleet now gone to Mytilene.