History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
And in the course of the same summer, not long afterwards, the people of Thespiae attacked the government but did not succeed; for succour came from Thebes and some were arrested, while others fled for refuge to Athens.
During the same summer the Syracusans, on learning that the Athenians had received their cavalry and that they were about to march against them immediately, thinking that unless the Athenians should get possession of Epipolae, a precipitous place lying directly above the city, they themselves, even if they were defeated in battle, could not easily be walled in, determined to guard the approaches to it, in order to prevent the enemy from ascending secretly by that way, since they could not possibly do so by any other road.
For at all other points the place overhangs the city and slopes right down to it, the whole height being visible from it; and it is called Epipolae by the Syracusans because it lies as an upper surface above the rest of the country.
So they went out at daybreak in full force to the meadow along the river Anapus—for Hermocrates and his fellow-generals, as it chanced, had just come into office—and proceeded to hold a review of the hoplites. And they selected first six hundred picked men of these, under the command of Diomilus, a fugitive from Andros, that these might be a guard for Epipolae, and if there were need of them anywhere else might be quickly at hand in a body.
And the Athenians during the night preceding the day on which the Syracusans held their review, came from Catana with their whole force and put in unobserved at the place called Leon, which is six or seven stadia distant from Epipolae, disembarking the land-force there and anchoring their ships at Thapsus. That is a peninsula, with a narrow isthmus, extending into the sea and not far distant from the city of Syracuse, either by sea or by land.
The naval force of the Athenians, having run a stockade across the isthmus, lay quiet on Thapsus; but the land-force advanced at once at a run to Epipolae, and got up by way of Euryelus before the Syracusans, when they became aware of it, could come up from the review which they were holding in the meadow.
They brought aid, however, everyone with what speed he could, the others as well as the six hundred under Diomilus; but they had not less than twenty-five stadia to go, after leaving the meadow, before they reached the enemy.