Syracuse, the most powerful state in Sicily, responded exceptionally slowly to the Athenian threat and, as a result, was almost completely invested before the arrival of back-up in the form of Spartan general Gylippus, who galvanized its inhabitants into action.

Thucydides observed that contemporary Greeks were shocked not that Athens eventually fell after the defeat, but rather that it fought on for as long as it did, so devastating were the losses suffered.

[15] In 425, the Athenians planned to reinforce their contingent with an additional forty triremes, but that fleet never reached Sicily, as it became caught up in the pivotal Battle of Pylos on the way there.

The terms of that peace, however, had never been fulfilled; Sparta had never surrendered Amphipolis to Athens, as required by the treaty, and in return the Athenians had held Pylos.

[24][25] At Athens, the Segestan ambassadors presented their case for intervention to the assembly, where debate over the proposal quickly divided along traditional factional lines.

The assembly eventually approved an expedition composed of sixty triremes, without hoplite accompaniment, commanded by Nicias, Alcibiades, and Lamachus.

[27] Nicias also attacked Alcibiades's credibility, claiming that he and his allies were inexperienced and self-aggrandizing young men eager to lead Athens into war for their own ends.

[29] The assembly was clearly leaning towards Alcibiades's side, so Nicias, judging them unlikely to cancel the expedition if he argued against it directly, chose a different tactic.

[30] Contrary to Nicias's plan, the assembly enthusiastically embraced his proposal, and passed a motion allowing the generals to arrange for a force of over 100 ships and 5,000 hoplites.

Alcibiades volunteered to be put on trial under penalty of death in order to prove his innocence (wanting to avoid his enemies charging him, in his absence, with more false information), but this request was denied.

Many people in Syracuse, the richest and most powerful city of Sicily, felt that the Athenians were in fact coming to attack them under the pretense of aiding Segesta in a minor war.

Lamachus, meanwhile, was a fifty-year-old career soldier, of whom the longest extant portrayal is a series of scenes in Aristophanes' The Acharnians that satirize him as a braggadocious, perpetually impoverished warrior.

[33] The reasons for the Athenians' choice are not recorded, but the assembly may have been seeking to balance the aggressive young leader with a more conservative older figure, with Lamachus added for his military expertise.

The fleet proceeded to Catania, where an Athenian ship arrived to inform Alcibiades that he was under arrest, not only for the destruction of the hermai, but also for supposedly profaning the Eleusinian Mysteries.

Alcibiades agreed to return in his ship, but when they stopped in southern Italy at Thurii, he escaped and sailed to the Peloponnese, where he sought refuge in Sparta.

The first contingent, commanded by Nicias, sailed to Segesta and forced the Segestans to pay the thirty talents they had promised the Athenians for their assistance against their rival Selinus.

The Athenians attacked first, believing themselves to be the stronger and more experienced army, and after some unexpectedly strong resistance, the Argives pushed back the Syracusan left wing, causing the rest to flee.

[44][2] Carthage opted to stay out of the conflict, but several Etruscan cities banded together and organized a small force to aid Athens.

The Athenian circumvallation, known as "the Circle", was meant to blockade Syracuse from the rest of the island, while the Syracusans built a number of counter-walls from the city to their various forts.

He wrote a letter to Athens, not trusting messengers to give an accurate report, and suggested that they either recall the expedition or send out massive reinforcements.

Nicias, who had opposed the expedition at first, now did not want to show any weakness either to the Syracusans and Spartans, or to the Athenians at home who he thought would have him executed, stating he would rather die by the hands of the enemy than by those of his countrymen.

Outside Syracuse, the Athenians built a smaller walled enclosure for their sick and injured, and put everyone else (including many of the soldiers remaining on land) on their ships for one last battle, on 9 September.

Javelin throwers and archers shot from each ship, but the Syracusans deflected Athenian grappling hooks by covering their decks with animal hides.

Seeing the vulnerable Athenians running from their beached vessels, Gylippus ordered a furious but disorganized attack on land to catch his enemies before they could reach their base.

Using this respite, the Athenians rallied and returned to fight alongside the Etruscans, securing several of their ships on the beach and preventing a complete catastrophe.

On the other side of the river a Syracusan force was waiting, and the Athenians were almost completely massacred, by far the worst defeat of the entire expedition in terms of lives lost.

Bury judged that by far the biggest single reason for the expedition's catastrophic failure was the incompetence of Nicias, aggravated by the recall of Alcibiades.

And he, giving no satisfactory account, was taken for a spreader of false intelligence and a disturber of the city, and was, therefore, fastened to the wheel and racked a long time, till other messengers arrived that related the whole disaster particularly.

Triremes could be replaced, but the 30,000 experienced oarsmen lost in Sicily were irreplaceable and Athens had to rely on ill-trained slaves to form the backbone of her new fleet.

[51] This expedition is portrayed in the real-time strategy video game Age of Empires II DE and its DLC Chronicles: Battle for Greece.