Thucydides, History of the Peloponnesian War
Benjamin Jowett, Ed.

64. The generals were aware of the state of affairs. They determined to draw the whole Syracusan¹ army as far as possible out of the city, and then in their absence sail thither by night and take up a convenient position unmolested. They knew that they would fail of their purpose² if they tried to disembark their men in the face of an enemy who was prepared to meet them, or if they marched openly by land and were discovered, for they had no cavalry of their own, and the Syracusan horse which were numerous would do great harm to their light-armed troops and the mass of attendants. Whereas if they sailed thither by night they would be enabled to take up a position in which the cavalry could do them no serious mischief.—The exact spot near the temple of Olympian Zeus which they afterwards occupied was indicated by Syracusan exiles who accompanied them.— Accordingly the generals devised the following plan; [2] they sent to Syracuse a man of whose fidelity they were assured, but whom the Syracusan leaders believed to be a friend of theirs. He was a Catanaean, and professed to come from adherents of their party whose names were familiar to them, and whom they knew to be still remaining in Catana³. [3] He told them that the Athenians lay within the city every night away from the camp in which their arms were deposited, and if at dawn on a set day the Syracusans with their whole force would come and attack the troops left in the camp, their partisans in Catana would themselves⁴ shut the Athenians up in the town c and fire their ships; meanwhile the Syracusans might assault the palisade, and easily take the camp-preparations had been made⁵, and many of the Catanaeans were in the plot; from them he came.