The Athenians made their preparations to retreat as secretly as possible, but the Syracusans soon discovered their plans. When they heard that their departure was delayed for twenty-seven days, they determined to attack the Athenian fleet once more, and again they were successful.
On land the Athenians repulsed Gylippus, but they gained little by this success, for the Syracusans had made up their mind that the whole Athenian army should be destroyed.
So, as Demosthenes had foreseen, they barricaded the entrance to the Great Harbour, drawing their ships across it and lashing them together with chains.
Nicias saw that a battle must be fought, and he ordered a great number of the land troops to go on board the fleet. At all costs he must strengthen his navy.
The first thing the Athenians had to do was to break through the ships that were lashed together at the mouth of the harbour. But before the chains could be broken the enemy was upon them, surrounding them on every side. Despair gave the Athenians courage, and so desperately did they fight that for a time it seemed that they might yet escape.
Above the crash of vessels rose the cheers or groans of those who watched the battle from the shore.
Thucydides gives us a picture of the hopes and fears, the triumph and despair of those who fought as of those who watched. He says:
"The fortune of the battle varied, and it was not possible that the spectators on the shore should all receive the same impression of it. Being quite close and having different points of view, they would some of them see their own ships victorious; their courage would then revive, and they would earnestly call upon the gods not to take from them their hope of deliverance. But others, who saw their ships worsted, cried and shrieked aloud, and were by the sight alone more utterly unnerved than the defeated combatants themselves.
"Others again who had fixed their gaze on some part of the struggle which was undecided were in a state of excitement still more terrible; they kept swaying their bodies to and fro in an agony of hope and fear, as the stubborn conflict went on and on; for at every instant they were all but saved or all but lost. And while the strife hung in the balance, you might hear in the Athenian army at once lamentation, shouting, cries of victory or defeat, and all the various sounds which are wrung from a great host in extremity of danger."
At length the Athenians were pushed back and yet further back, until the fleet was stranded on the shore. The soldiers who had been left on land now rushed forward and succeeded in saving sixty of their ships from the enemy.
Demosthenes urged the men to embark and try once again to cut their way out of the harbour, but they refused, so crushed were they by their defeat. To retreat by land was all that the Athenians could now try to do, yet in their hearts they knew that the retreat must end in slavery or in death.
The sick and the wounded were left behind. But those who were stricken with fever, caused by the marsh land on which they had been encamped, clung to their comrades, and scarce knowing what they did, begged that they might not be left behind. But their strength soon failed, and they sank down by the wayside to die.
Nicias, ill as he was, did all in his power to encourage and cheer his men. He himself led the van, Demosthenes brought up the rear.
After marching for several days, the Athenians were parched with thirst. When at length they reached a stream, it was to find the enemy awaiting them on the farther bank.
But their thirst was intolerable, and paying no heed to the foe, the soldiers rushed to the water. As they stooped to drink, the Syracusans fell upon them and put them to death.
Demosthenes and his men had fallen behind the rest of the army, and had already been forced to surrender. Nicias now saw that he, too, must submit to Gylippus.
Seven thousand prisoners were sent by the Spartans to work in stone quarries. These quarries were like dungeons, but they were open to the sky, and during the day the scorching sun beat down piteously on the miserable prisoners, while at night the cold was so intense that sleep was impossible.
Here they were kept for seventy days, with only enough food to keep them alive, and with scarcely any water to drink. Many of the men died, those who survived were sold as slaves.
Nicias and Demosthenes were both put to death. It is said that they were tortured, although Gylippus did all he could to save them from the angry Syracusans. Thus in disaster and defeat ended the expedition that sailed forth so bravely from Athens two years before.
Thucydides says that this expedition was "the greatest adventure that the Greeks entered into during this war, and, in my opinion," he adds, "the greatest in which the Greeks were ever concerned; the one most splendid for the conquerors and most disastrous for the conquered, for they suffered no common defeat, but were absolutely annihilated—land-army, fleet and all—and of many thousands only a handful ever returned home."