By the capture of Plemmyrium a great treasure fell into the hands of the Syracusans. The loss to the Athenians, in money, stores, and men, was serious enough; but further consequences ensued, which were nothing less than disastrous. The enemy now commanded both sides of the entrance to the Great Harbour, and not a ship-load of provisions could reach the Athenian camp without an encounter with the Syracusan triremes. Well might despondency and dismay take possession of the beleaguered army, cramped in their narrow quarters on the swampy flats of the Anapus.
All Sicily, with one or two exceptions, had now declared for Syracuse, and reinforcements came pouring in from every side. Gylippus was resolved, if possible, to destroy the armament of Nicias, before the fresh succours from Athens had time to arrive; and, as before, the attack was to be made simultaneously by sea and land. Since the loss of Plemmyrium, the Athenian fleet had been penned up in the confined space at the head of the Great Harbour. Outside of these narrow limits, the whole coast was in the hands of the enemy, and any Athenian trireme which ventured out into open water ran the risk of being driven on a hostile shore. Unless they chose to incur this great peril, the Athenians would have to fight in close order, with the long, tapering prows of their vessels exposed to collision.
The Syracusans skilfully availed themselves of the advantage thus offered. The impact of prow with prow, which had hitherto been regarded as a disgraceful evidence of bad seamanship, had now become the most effective method of attack; and in order to execute this simple manoeuvre without damage to their own ships, the Syracusans shortened the prows of their triremes, and strengthened them with heavy beams of timber, thus converting them into a broad and solid mass, which could be driven with crushing force against the slender beaks of the Athenian galleys.
When all was ready, Gylippus led out his troops, and assailed the Athenian wall which faced towards Syracuse, and at the same time the garrison stationed at Polichne left their quarters, and made another attack on the opposite side. The assault had already commenced, when the Syracusan fleet, which numbered eighty triremes, was seen advancing towards the inner shore of the bay, where the ships of Nicias lay moored; and the Athenian seamen, who had not expected to be called into action, hastened in some confusion to man their ships, seventy-five of which were presently engaged with the enemy. After a day passed in irregular and desultory fighting, the battle ended slightly in favour of the Syracusans. During the next day the Syracusans remained inactive, and Nicias employed the interval in repairing the ships which had suffered damage, and providing for the defence of his fleet. The Athenian naval station was protected by a row of piles, rammed into the bottom of the sea, forming a semi-circular breastwork, with an opening about two hundred feet wide, where the ships passed in and out. On either side of this entrance Nicias caused a merchant vessel to be moored, and each vessel was provided with an engine called a dolphin, a heavy mass of lead, suspended from the yard-arm, which could be dropped on the deck of any hostile trireme attempting to pass.