Three months had now been frittered away in Sicily, during which the Athenians had done little or nothing, if we except the acquisition of Naxos and Catana. Nicias now resolved to make an attempt upon Syracuse. By a false message that the Catanaeans were ready to assist in expelling the Athenians, he induced the Syracusans to proceed thither in great force, and he availed himself of their absence to sail with his whole fleet into the Great Harbour of Syracuse, where he landed near the mouth of the Anapus. The Syracusans, when they found that they had been deceived at Catana, marched back and offered Nicias battle in his new position. The latter accepted it, and gained the victory; after which he retired to Catana, and subsequently to Naxos into winter quarters.

The Syracusans employed the winter in preparations for defence. They also despatched envoys to Corinth and Sparta to solicit assistance, in the latter of which towns they found an unexpected advocate. Alcibiades, having crossed from Thurii to Cyllene in Peloponnesus, received a special invitation to proceed to Sparta. Here he revealed all the plans of Athens, and exhorted the Lacedaemonians to frustrate them. For this purpose he advised them to send an army into Sicily, under the command of a Spartan general, and, by way of causing a diversion, to establish a fortified post at Decelea in the Attic territory. The Spartans fell in with these views, and resolved to send a force to the assistance of Syracuse in the spring, under the command of Gylippus.

Nicias, having received reinforcements from Athens, recommenced hostilities as soon as the season allowed of it, and resolved on besieging Syracuse. That town consisted of two parts--the inner and the outer city. The former of these--the original settlement was comprised in the island of Ortygia; the latter afterwards known by the name of Achradina, covered the high ground of the peninsula north of Ortygia, and was completely separate from the inner city. The island of Ortygia, to which the modern city is now confined, is of an oblong shape, about two miles in circumference, lying between the Great Harbour on the west, and the Little Harbour on the east, and separated from the mainland by a narrow channel. The Great Harbour is a splendid bay, about five miles in circumference, and the Little Harbour was spacious enough to receive a large fleet of ships of war. The outer city was surrounded on the north and east by the sea and by sea-walls which rendered an assault on that side almost impracticable. On the land side it was defended by a wall, and partly also by the nature of the ground, which in some part was very steep. West and north-west of the wall of the outer city stood two unfortified suburbs, which were at a later time included within the walls of Syracuse under the names of Tyche and Neapolis. Between these two suburbs the ground rose in a gentle acclivity to the summit of the ranges of hills called Epipolae.

It was from the high ground of Epipolae that Syracuse was most exposed to attack. Nicias landed at Leon, a place upon the bay of Thapsus, at the distance of only six or seven stadia from Epipolae, took possession of Epipolae, and erected on the summit a fort called Labdalum. Then coming farther down the hill towards Syracuse, he built another fort of a circular form and of considerable size at a place called Syke. From the latter point he commenced his line of circumvallation, one wall extending southwards from Syke to the Great Harbour, and the other wall running northwards to the outer sea. The Athenians succeeded in completing the circumvallation towards the south, but in one of their many engagements with the Syracusans they lost the gallant Lamachus. At the same time, the Athenian fleet entered the Great Harbour, where it was henceforth permanently established. The northern wall was never completed, and through the passage thus left open the besieged continued to obtain provisions. Nicias, who, by the death of Lamachus, had become sole commander, seemed now on the point of succeeding. The Syracusans were so sensible of their inferiority in the field that they no longer ventured to show themselves outside the walls. They began to contemplate surrender, and even sent messages to Nicias to treat of the terms. This caused the Athenian commander to indulge in a false confidence of success, and consequent apathy; and the army having lost the active and energetic Lamachus, operations were no longer carried on with the requisite activity.

It was in this state of affairs that the Spartan commander, Gylippus, passed over into Italy with a little squadron of four ships, with the view merely of preserving the Greek cities in that country, supposing that Syracuse, and, with her, the other Greek cities in Sicily, were irretrievably lost. At Tarentum he learned to his great surprise and satisfaction that the Athenian wall of circumvallation at Syracuse had not yet been completed on the northern side. He now sailed through the straits of Messana, which were left completely unguarded, and arrived safely at Himera on the north coast of Sicily. Here he announced himself as the forerunner of larger succours, and began to levy an army which the magic of the Spartan name soon enabled him to effect; and in a few days he was in a condition to march towards Syracuse with about 3000 men. The Syracusans now dismissed all thoughts of surrender, and went out boldly to meet Gylippus, who marched into Syracuse over the heights of Epipolae, which the supineness of Nicias had left unguarded. Upon arriving in the city, Gylippus sent a message to the Athenians allowing them a five days' truce to collect their effects and evacuate the island. Nicias returned no answer to this insulting proposal; but the operations of Gylippus soon showed that the tide of affairs was really turned. His first exploit was to capture the Athenian fort at Labdalum, which made him master of Epipolae. He next commenced constructing a counter-wall to intersect the Athenian lines on the northern side. This turn of affairs induced those Sicilian cities which had hitherto hesitated to embrace the side of Syracuse. Gylippus was also reinforced by the arrival of thirty triremes from Corinth, Leucas, and Ambracia. Nicias now felt that the attempt to blockade Syracuse with his present force was hopeless. He therefore resolved to occupy the headland of Plemmyrium, the southernmost point of the entrance to the Great Harbour, which would be a convenient station for watching the enemy, as well as for facilitating the introduction of supplies. Here he accordingly erected three forts and formed a naval station. Some slight affairs occurred in which the balance of advantage was in favour of the Syracusans. By their change of station the Athenians were now a besieged rather than a besieging force. Their triremes were becoming leaky, and their soldiers and sailors were constantly deserting. Nicias himself had fallen into a bad state of health; and in this discouraging posture of affairs he wrote to Athens requesting to he recalled, and insisting strongly on the necessity of sending reinforcements.

The Athenians refused to recall Nicias, but they determined on sending a large reinforcement to Sicily, under the joint command of Demosthenes and Eurymedon. The news of these fresh and extensive preparations incited the Lacedaemonians to more vigorous action. The peace, if such it can be called, was now openly broken; and in the spring of 413 B.C. the Lacedaemonians, under King Agis, invaded Attica itself, and, following the advice of Alcibiades, established themselves permanently at Decelia, a place situated on the ridge of Mount Parnes about 14 miles north of Athens, and commanding the Athenian plain. The city was thus placed in a state of siege. Scarcity began to be felt within the walls; the revenues were falling off, whilst on the other hand expenses were increasing.

Meanwhile in Sicily the Syracusans had gained such confidence that they even ventured on a naval engagement with the Athenians. In the first battle the Athenians were victorious, but the second battle, which lasted two days, ended in their defeat. They were now obliged to haul up their ships in the innermost part of the Great Harbour, under the lines of their fortified camp. A still more serious disaster than the loss of the battle was the loss of their naval reputation. It was evident that the Athenians had ceased to be invincible on the sea; and the Syracusans no longer despaired of overcoming them on their own element.

Such was the state of affairs when, to the astonishment of the Syracusans, a fresh Athenian fleet of 75 triremes, under Demosthenes and Eurymedon, entered the Great Harbour with all the pomp and circumstance of war. It had on board a force of 5000 hoplites, of whom about a quarter were Athenians, and a great number of light-armed troops. The active and enterprising character of Demosthenes led him to adopt more vigorous measures than those which had been hitherto pursued. He saw at once that whilst Epipolae remained in the possession of the Syracusans there was no hope of taking their city, and he therefore directed all his efforts to the recapture of that position. But his attempts were unavailing. He was defeated not only in an open assault upon the Syracusan wall, but in a nocturnal attempt to carry it by surprise. These reverses were aggravated by the breaking out of sickness among the troops. Demosthenes now proposed to return home and assist in expelling the Lacedaemonians from Attica, instead of pursuing an enterprise which seemed to be hopeless. But Nicias, who feared to return to Athens with the stigma of failure, refused to give his consent to this step. Demosthenes then urged Nicias at least to sail immediately out of the Great Harbour, and take up their position either at Thapsus or Catana, where they could obtain abundant supplies of provisions, and would have an open sea for the manoeuvres of their fleet. But even to this proposal Nicias would not consent; and the army and navy remained in their former position. Soon afterwards, however, Gylippus received such large reinforcements, that Nicias found it necessary to adopt the advice of his colleague. Preparations were secretly made for their departure, the enemy appear to have had no suspicion of their intention and they were on the point of quitting their ill- fated quarters on the following morning, when on the very night before (27 Aug. 413 B.C.) an eclipse of the moon took place. The soothsayers who were consulted said that the army must wait thrice nine days, a full circle of the moon, before it could quit its present position; and the devout and superstitious Nicias forthwith resolved to abide by this decision.