History of the Peloponnesian War

However, the Athenians, distressed by the plague, and by the war that had recently broken out and was now raging, thought it a serious matter to add Lesbos with its fleet and untouched resources to the list of their enemies; and at first would not believe the charge, giving too much weight to their wish that it might not be true. But when an embassy which they sent had failed to persuade the Mitylenians to give up the union and preparations complained of, they became alarmed, and resolved to strike the first blow.

They accordingly suddenly sent off forty ships that had been got ready to sail round Peloponnese, under the command of Cleippides, son of Deinias, and two others;

word having been brought them of a festival in honor of the Malean Apollo outside the town, which is kept by the whole people of Mitylene, and at which, if haste were made, they might hope to take them by surprise. If this plan succeeded, well and good; if not, they were to order the Mitylenians to deliver up their ships and to pull down their walls, and if they did not obey, to declare war.