History of the Peloponnesian War

As for all the other prisoners of the Athenians and their confederates, they put them into the quarries as the safest custody. But Nicias and Demosthenes they killed, against Gylippus' will. For Gylippus thought the victory would be very honourable if, over and above all his other success, he could carry home both the generals of the enemy to Lacedaemon.

And it fell out that one of them, Demosthenes, was their greatest enemy for the things he had done in the island and at Pylus; and the other, upon the same occasion, their greatest friend. For Nicias had earnestly laboured to have those prisoners which were taken in the island to be set at liberty by persuading the Athenians to the peace.

For which cause the Lacedaemonians were inclined to love him; and it was principally in confidence of that that he rendered himself to Gylippus. But certain Syracusians, as it is reported, some of them for fear (because they had been tampering with him) lest being put to the torture he might bring them into trouble, whereas now they were well enough; and others, especially the Corinthians, fearing he might get away by corruption of one or other, being wealthy, and work them some mischief afresh, having persuaded their confederates to the same, killed him.

For these, or for causes near unto these, was he put to death; being the man that, of all the Grecians of my time, had least deserved to be brought to so great a degree of misery.

As for those in the quarries, the Syracusians handled them at first but ungently. For in this hollow place, first the sun and suffocating air (being without roof) annoyed them one way; and on the other side, the nights coming upon that heat, autumnal and cold, put them, by reason of the alteration, into strange diseases;