As soon as it was day, Nicias led his troops forward; while the Syracusans and allies pressed on them in the same manner, discharging their missiles at them, and striking them down with their javelins on every side. The Athenians were hurrying on to reach the river Assinarus, being urged to this at once by the attack made on every side of them by the numerous cavalry and the rest of the light-armed multitude (for they thought they should be more at ease if they were once across the river), and also by their weariness and craving for drink. When they reached its banks, they rushed into it without any more regard for order, every man anxious to be himself the first to cross it; while the attack of the enemy rendered the passage more difficult. For being compelled to advance in a dense body, they fell upon and trod down one another; and some of them died immediately on the javelins and articles of baggage, while others were entangled together, and floated down the stream. On the other side of the river, too, the Syracusans lined the bank, which was precipitous, and from the higher ground discharged their missiles on the Athenians, while most of them were eagerly drinking in confusion amongst themselves in the hollow bed of the stream. The Peloponnesians, moreover, charged them and butchered them, especially those in the river. And thus the water was immediately spoiled; but nevertheless it was drunk by them, mud and all, and bloody as it was, it was even fought for by most of them.
At length, when many dead were now heaped one upon another in the river, and the army was destroyed, either at the river, or, if any part had escaped, by the cavalry, Nicias surrendered himself to Gylippus, placing more confidence in him than in the Syracusans; and desired him and the Lacedæmonians to do what they pleased with himself, but to stop butchering the rest of the soldiers. After this, Gylippus commanded to make prisoners; and they collected all that were alive, excepting such as they concealed for their own benefit (of whom there was a large number). They also sent a party in pursuit of the three hundred, who had forced their way through the sentinels during the night, and took them. The part of the army, then, that was collected as general property, was not large, but that which was secreted was considerable; and the whole of Sicily was filled with them, inasmuch as they had not been taken on definite terms of surrender, like those with Demosthenes. Indeed no small part was actually put to death; for this was the most extensive slaughter, and surpassed by none of all that occurred in this Sicilian war. In the other encounters also, which were frequent on their march, no few had fallen. But many also escaped; some at the moment, others after serving as slaves, and running away subsequently. These found a place of refuge at Catana.
When the Syracusans and allies were assembled together, they took with them as many prisoners as they could, with the spoils, and returned to the city. All the rest of the Athenians and the allies that they had taken, they sent down into the quarries, thinking this the safest way of keeping them; but Nicias and Demosthenes they executed, against the wish of Gylippus. For he thought it would be a glorious distinction for him, in addition to all his other achievements, to take to the Lacedæmonians the generals who had commanded against them. And it so happened, that one of these, namely Demosthenes, was regarded by them as their most inveterate enemy, in consequence of what had occurred on the island and at Pylos; the other, for the same reasons, as most in their interest; for Nicias had exerted himself for the release of the Lacedæmonians taken from the island, by persuading the Athenians to make a treaty. On this account the Lacedæmonians had friendly feelings towards him; and indeed it was mainly for the same reasons that he reposed confidence in Gylippus, and surrendered himself to him. But certain of the Syracusans (as it was said) were afraid, some of them, since they had held communication with him, that if put to the torture, he might cause them trouble on that account in the midst of their success; others, and especially the Corinthians, lest he might bribe some, as he was rich, and effect his escape, and so they should again incur mischief through his agency; and therefore they persuaded the allies, and put him to death. For this cause then, or something very like it, he was executed, having least of all the Greeks deserved to meet with such a misfortune, on account of his devoted attention to the practice of every virtue.