In the meantime, after he had left Sicily, Nikias was so cautious that the Syracusans thought him cowardly, and provoked a battle with him close to their own walls.  He defeated them, besieged their city, and had almost taken it, when a Spartan and Corinthian fleet, headed by Gylippus, came out, forced their way through the Athenians, and brought relief to the city.  More reinforcements came out to Athens, and there was a great sea-fight in front of the harbour at Syracuse, which ended in the total and miserable defeat of the Athenians, so that the army was obliged to retreat from Syracuse, and give up the siege.  They had no food, nor any means of getting home, and all they could do was to make their way back into the part of the island that was friendly to them.  Gylippus and the Syracusans tried to block their way, but old Nikias showed himself firm and undaunted in the face of misfortune, and they forced their way on for three or four days, in great suffering from hunger and thirst, till at last they were all hemmed into a small hollow valley, shut in by rocks, where the Syracusans shot them down as they came to drink at the stream, so thirsty that they seemed not to care to die so long as they could drink.  Upon this, Nikias thought it best to offer to lay down his arms and surrender.  All the remnant of the army were enclosed in a great quarry at Epipolæ, the sides of which were 100 feet high, and fed on a scanty allowance of bread and water, while the victors considered what was to be done with them, for in these heathen times there was no law of mercy for a captive, however bravely he might have fought.  Gylippus wanted to save Nikias, for the pleasure of showing off so noble a prisoner at Sparta; but some of the Syracusans, who had been on the point of betraying their city to him, were afraid that their treason would be known, and urged that he should be put to death with his fellow-general; and the brave, honest, upright old man was therefore slain with his companion Demosthenes.