During this time the Athenians were not idle. Simultaneously with the fortification of Decelea, at the very beginning of spring, they sent thirty ships round Peloponnese, under Charicles, son of Apollodorus, with instructions to call at Argos and demand a force of their heavy infantry for the fleet, agreeably to the alliance. At the same time they dispatched Demosthenes to Sicily, as they had intended, with sixty Athenian and five Chian vessels, twelve hundred Athenian heavy infantry from the muster-roll, and as many of the islanders as could be raised in the different quarters, drawing upon the other subject allies for whatever they could supply that would be of use for the war. Demosthenes was instructed first to sail round with Charicles and to operate with him upon the coasts of Laconia, and accordingly sailed to Aegina and there waited for the remainder of his armament, and for Charicles to fetch the Argive troops.

In Sicily, about the same time in this spring, Gylippus came to Syracuse with as many troops as he could bring from the cities which he had persuaded to join. Calling the Syracusans together, he told them that they must man as many ships as possible, and try their hand at a sea-fight, by which he hoped to achieve an advantage in the war not unworthy of the risk. With him Hermocrates actively joined in trying to encourage his countrymen to attack the Athenians at sea, saying that the latter had not inherited their naval prowess nor would they retain it for ever; they had been landsmen even to a greater degree than the Syracusans, and had only become a maritime power when obliged by the Mede. Besides, to daring spirits like the Athenians, a daring adversary would seem the most formidable; and the Athenian plan of paralysing by the boldness of their attack a neighbour often not their inferior in strength could now be used against them with as good effect by the Syracusans. He was convinced also that the unlooked-for spectacle of Syracusans daring to face the Athenian navy would cause a terror to the enemy, the advantages of which would far outweigh any loss that Athenian science might inflict upon their inexperience. He accordingly urged them to throw aside their fears and to try their fortune at sea; and the Syracusans, under the influence of Gylippus and Hermocrates, and perhaps some others, made up their minds for the sea-fight and began to man their vessels.

When the fleet was ready, Gylippus led out the whole army by night; his plan being to assault in person the forts on Plemmyrium by land, while thirty-five Syracusan galleys sailed according to appointment against the enemy from the great harbour, and the forty-five remaining came round from the lesser harbour, where they had their arsenal, in order to effect a junction with those inside and simultaneously to attack Plemmyrium, and thus to distract the Athenians by assaulting them on two sides at once. The Athenians quickly manned sixty ships, and with twenty-five of these engaged the thirty-five of the Syracusans in the great harbour, sending the rest to meet those sailing round from the arsenal; and an action now ensued directly in front of the mouth of the great harbour, maintained with equal tenacity on both sides; the one wishing to force the passage, the other to prevent them.

In the meantime, while the Athenians in Plemmyrium were down at the sea, attending to the engagement, Gylippus made a sudden attack on the forts in the early morning and took the largest first, and afterwards the two smaller, whose garrisons did not wait for him, seeing the largest so easily taken. At the fall of the first fort, the men from it who succeeded in taking refuge in their boats and merchantmen, found great difficulty in reaching the camp, as the Syracusans were having the best of it in the engagement in the great harbour, and sent a fast-sailing galley to pursue them. But when the two others fell, the Syracusans were now being defeated; and the fugitives from these sailed alongshore with more ease. The Syracusan ships fighting off the mouth of the harbour forced their way through the Athenian vessels and sailing in without any order fell foul of one another, and transferred the victory to the Athenians; who not only routed the squadron in question, but also that by which they were at first being defeated in the harbour, sinking eleven of the Syracusan vessels and killing most of the men, except the crews of three ships whom they made prisoners. Their own loss was confined to three vessels; and after hauling ashore the Syracusan wrecks and setting up a trophy upon the islet in front of Plemmyrium, they retired to their own camp.

Unsuccessful at sea, the Syracusans had nevertheless the forts in Plemmyrium, for which they set up three trophies. One of the two last taken they razed, but put in order and garrisoned the two others. In the capture of the forts a great many men were killed and made prisoners, and a great quantity of property was taken in all. As the Athenians had used them as a magazine, there was a large stock of goods and corn of the merchants inside, and also a large stock belonging to the captains; the masts and other furniture of forty galleys being taken, besides three galleys which had been drawn up on shore. Indeed the first and chiefest cause of the ruin of the Athenian army was the capture of Plemmyrium; even the entrance of the harbour being now no longer safe for carrying in provisions, as the Syracusan vessels were stationed there to prevent it, and nothing could be brought in without fighting; besides the general impression of dismay and discouragement produced upon the army.

After this the Syracusans sent out twelve ships under the command of Agatharchus, a Syracusan. One of these went to Peloponnese with ambassadors to describe the hopeful state of their affairs, and to incite the Peloponnesians to prosecute the war there even more actively than they were now doing, while the eleven others sailed to Italy, hearing that vessels laden with stores were on their way to the Athenians. After falling in with and destroying most of the vessels in question, and burning in the Caulonian territory a quantity of timber for shipbuilding, which had been got ready for the Athenians, the Syracusan squadron went to Locri, and one of the merchantmen from Peloponnese coming in, while they were at anchor there, carrying Thespian heavy infantry, took these on board and sailed alongshore towards home. The Athenians were on the look-out for them with twenty ships at Megara, but were only able to take one vessel with its crew; the rest getting clear off to Syracuse. There was also some skirmishing in the harbour about the piles which the Syracusans had driven in the sea in front of the old docks, to allow their ships to lie at anchor inside, without being hurt by the Athenians sailing up and running them down. The Athenians brought up to them a ship of ten thousand talents burden furnished with wooden turrets and screens, and fastened ropes round the piles from their boats, wrenched them up and broke them, or dived down and sawed them in two. Meanwhile the Syracusans plied them with missiles from the docks, to which they replied from their large vessel; until at last most of the piles were removed by the Athenians. But the most awkward part of the stockade was the part out of sight: some of the piles which had been driven in did not appear above water, so that it was dangerous to sail up, for fear of running the ships upon them, just as upon a reef, through not seeing them. However divers went down and sawed off even these for reward; although the Syracusans drove in others. Indeed there was no end to the contrivances to which they resorted against each other, as might be expected between two hostile armies confronting each other at such a short distance: and skirmishes and all kinds of other attempts were of constant occurrence. Meanwhile the Syracusans sent embassies to the cities, composed of Corinthians, Ambraciots, and Lacedaemonians, to tell them of the capture of Plemmyrium, and that their defeat in the sea-fight was due less to the strength of the enemy than to their own disorder; and generally, to let them know that they were full of hope, and to desire them to come to their help with ships and troops, as the Athenians were expected with a fresh army, and if the one already there could be destroyed before the other arrived, the war would be at an end.

While the contending parties in Sicily were thus engaged, Demosthenes, having now got together the armament with which he was to go to the island, put out from Aegina, and making sail for Peloponnese, joined Charicles and the thirty ships of the Athenians. Taking on board the heavy infantry from Argos they sailed to Laconia, and, after first plundering part of Epidaurus Limera, landed on the coast of Laconia, opposite Cythera, where the temple of Apollo stands, and, laying waste part of the country, fortified a sort of isthmus, to which the Helots of the Lacedaemonians might desert, and from whence plundering incursions might be made as from Pylos. Demosthenes helped to occupy this place, and then immediately sailed on to Corcyra to take up some of the allies in that island, and so to proceed without delay to Sicily; while Charicles waited until he had completed the fortification of the place and, leaving a garrison there, returned home subsequently with his thirty ships and the Argives also.

This same summer arrived at Athens thirteen hundred targeteers, Thracian swordsmen of the tribe of the Dii, who were to have sailed to Sicily with Demosthenes. Since they had come too late, the Athenians determined to send them back to Thrace, whence they had come; to keep them for the Decelean war appearing too expensive, as the pay of each man was a drachma a day. Indeed since Decelea had been first fortified by the whole Peloponnesian army during this summer, and then occupied for the annoyance of the country by the garrisons from the cities relieving each other at stated intervals, it had been doing great mischief to the Athenians; in fact this occupation, by the destruction of property and loss of men which resulted from it, was one of the principal causes of their ruin. Previously the invasions were short, and did not prevent their enjoying their land during the rest of the time: the enemy was now permanently fixed in Attica; at one time it was an attack in force, at another it was the regular garrison overrunning the country and making forays for its subsistence, and the Lacedaemonian king, Agis, was in the field and diligently prosecuting the war; great mischief was therefore done to the Athenians. They were deprived of their whole country: more than twenty thousand slaves had deserted, a great part of them artisans, and all their sheep and beasts of burden were lost; and as the cavalry rode out daily upon excursions to Decelea and to guard the country, their horses were either lamed by being constantly worked upon rocky ground, or wounded by the enemy.

Besides, the transport of provisions from Euboea, which had before been carried on so much more quickly overland by Decelea from Oropus, was now effected at great cost by sea round Sunium; everything the city required had to be imported from abroad, and instead of a city it became a fortress. Summer and winter the Athenians were worn out by having to keep guard on the fortifications, during the day by turns, by night all together, the cavalry excepted, at the different military posts or upon the wall. But what most oppressed them was that they had two wars at once, and had thus reached a pitch of frenzy which no one would have believed possible if he had heard of it before it had come to pass. For could any one have imagined that even when besieged by the Peloponnesians entrenched in Attica, they would still, instead of withdrawing from Sicily, stay on there besieging in like manner Syracuse, a town (taken as a town) in no way inferior to Athens, or would so thoroughly upset the Hellenic estimate of their strength and audacity, as to give the spectacle of a people which, at the beginning of the war, some thought might hold out one year, some two, none more than three, if the Peloponnesians invaded their country, now seventeen years after the first invasion, after having already suffered from all the evils of war, going to Sicily and undertaking a new war nothing inferior to that which they already had with the Peloponnesians? These causes, the great losses from Decelea, and the other heavy charges that fell upon them, produced their financial embarrassment; and it was at this time that they imposed upon their subjects, instead of the tribute, the tax of a twentieth upon all imports and exports by sea, which they thought would bring them in more money; their expenditure being now not the same as at first, but having grown with the war while their revenues decayed.

Accordingly, not wishing to incur expense in their present want of money, they sent back at once the Thracians who came too late for Demosthenes, under the conduct of Diitrephes, who was instructed, as they were to pass through the Euripus, to make use of them if possible in the voyage alongshore to injure the enemy. Diitrephes first landed them at Tanagra and hastily snatched some booty; he then sailed across the Euripus in the evening from Chalcis in Euboea and disembarking in Boeotia led them against Mycalessus. The night he passed unobserved near the temple of Hermes, not quite two miles from Mycalessus, and at daybreak assaulted and took the town, which is not a large one; the inhabitants being off their guard and not expecting that any one would ever come up so far from the sea to molest them, the wall too being weak, and in some places having tumbled down, while in others it had not been built to any height, and the gates also being left open through their feeling of security. The Thracians bursting into Mycalessus sacked the houses and temples, and butchered the inhabitants, sparing neither youth nor age, but killing all they fell in with, one after the other, children and women, and even beasts of burden, and whatever other living creatures they saw; the Thracian race, like the bloodiest of the barbarians, being even more so when it has nothing to fear. Everywhere confusion reigned and death in all its shapes; and in particular they attacked a boys’ school, the largest that there was in the place, into which the children had just gone, and massacred them all. In short, the disaster falling upon the whole town was unsurpassed in magnitude, and unapproached by any in suddenness and in horror.