Plutarch, Nicias
Bernadotte Perrin, Ed.

Now in most actions Nicias took part, despite his bodily infirmity. But once, when his weakness was extreme, he was lying in bed within the walls, attended by a few servants, while Lamachus with the soldiery was fighting the Syracusans. These were trying to run a wall from their city out to that which the Athenians were building, to inter- sect it and prevent its completion. [2] The Athenians prevailed, and hurried off in pursuit with more or less disorder, so that Lamachus was isolated, and then had to face some Syracusan horsemen who made an onset upon him. Foremost of these was Callicrates, a man skilled in war and of a high courage. Lamachus accepted his challenge to single combat, fought him, got a mortal blow from him, but gave him back the like, and fell and died along with him. [3] The Syracusans got possession of the body of Lamachus, with its armour, and carried it off. Then they made a dash upon the Athenian walls where Nicias was, with none to succour him. He nevertheless, necessity compelling him, rose from his bed, saw his peril, and ordered his attendants to bring fire and set it to all the timbers that lay scattered in front of the walls for the construction of siege-engines, and to the engines themselves. This brought the Syracusans to a halt, and saved Nicias as well as the walls and stores of the Athenians. For when the Syracusans saw a great flame rising between them and the walls, they withdrew. [4]

Thus it came to pass that Nicias was left sole general; but he was in great hopes. Cities were inclining to take his side, and ships full of grain came to his camp from every quarter. Everybody hastens to join a successful cause. Besides, sundry proposals for a treaty were already coming to him from those Syracusans who despaired of their city. [5] At this time, too, Gylippus, who was sailing from Sparta to their aid, when he heard on his voyage how they were walled up and in sore distress, held on his way, it is true, but with the belief that Sicily was as good as taken, and that he could only save the cities of the Italian Greeks, if haply even that. For the opinion gained ground and strength that the Athenians were all powerful, and had a general who was invincible by reason of his judgement and good fortune. [6]

And Nicias himself, contrary to his nature, was straightway so emboldened by the present momentum of his good fortune, and, most of all, by the secret messengers sent to him from the Syracusans was so fixed i his belief that the city was just on the point of surrendering conditionally, that he made no sort of account of Gylippus at his approach. He did not even set an adequate watch against him. Wherefore, finding himself completely overlooked and despised, the man sailed stealthily through the straits, made a landing at the farthest point from Syracuse, and collected a large force, the Syracusans being not so much as aware of his presence, nor even expecting him. [7] On the contrary, they had actually called an assembly to discuss the agreements to be made with Nicias, and some were already on their way to it, thinking that the terms of peace should be made before their city was completely walled up. For that part of the work which remained to be done was quite small, and all the material required for it lay strewn along the line.