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.
Meanwhile the Athenian generals were deliberating about the situation in view both of the calamity that had happened and of the utter discouragement that now prevailed in the army. They saw that they were not succeeding in their undertaking, and that the soldiers were finding their stay burdensome.
For they were distressed by sickness for a double cause, the season of the year being that in which men are most liable to illness, while at the same time the place in which they were encamped was marshy and unhealthy; and the situation in general appeared to them to be utterly hopeless.
Demosthenes, therefore, was of the opinion that they should not remain there any longer, but since the plan which had induced him to risk the attack upon Epipolae had failed, his vote was for going away without loss of time, while it was still possible to cross the sea and to have some superiority over the enemy with at any rate the ships of the armament which had come to reinforce them.
From the point of view of the State, also, he said, it was more profitable to carry on the war against the enemy who were building a hostile fortress in their own territory than against the Syracusans, whom it was no longer easy to conquer; and furthermore, it was not right that they should continue the siege and spend a great deal of money to no purpose.
Such was the judgment of Demosthenes. Nicias, however, although he also thought that their situation was bad, did not wish expressly to reveal their weakness, or that they should be reported to the enemy as openly voting in full council for the retreat; for, he urged, they would be far less likely, when they should wish to retreat, to do this unobserved.
Besides, the affairs of the enemy, from such information as he had beyond the rest, still afforded some hope that they would turn out to be worse than their own, if they persisted in the siege; for they would wear the enemy out by cutting off his supplies, especially since now with their present fleet they were to a greater extent than before the masters of the sea. And, in fact, there was a party in Syracuse that favoured submitting to the Athenians, and it was secretly sending proposals to him and urging him not to withdraw. Having knowledge of these things, although in reality he still wavered between the two alternatives and kept pondering them, yet in the speech which he openly made at that time he refused to lead the army away.