History of the Peloponnesian War

When, on consideration of this, it appeared a difficulty to the magistrates, and Hermocrates could not then prevail upon them to attempt it, he afterwards devised the following scheme. Being afraid that the Athenians might get the start of them by quietly passing during the night the most difficult points of the country, he sent certain of his own friends with some cavalry to the Athenian camp, as soon as it grew dark. These, riding up to within hearing, and calling to them certain individuals, as though they were friends of the Athenians, (for there were some who sent tidings to Nicias of what passed within the city,) desired them to tell that general not to lead off his army by night, as the Syracusans were guarding the roads; but to retire leisurely by day after making his preparations.

They then, after delivering this message, returned; while those who heard it, reported the same to the Athenian generals.