Peace was declined, and it was resolved to prosecute in earnest the siege of the two Sicilian cities and for this purpose to send to sea once more a fleet of 200 sail. The siege of Lilybaeum, the first great and regular siege undertaken by Rome, and one of the most obstinate known in history, was opened by the Romans with an important success: they succeeded in introducing their fleet into the harbour of the city, and in blockading it on the side facing the sea. The besiegers, however, were not able to close the sea completely. In spite of their sunken vessels and their palisades, and in spite of the most careful vigilance, dexterous mariners, accurately acquainted with the shallows and channels, maintained with swift-sailing vessels a regular communication between the besieged in the city and the Carthaginian fleet in the harbour of Drepana. In fact after some time a Carthaginian squadron of 50 sail succeeded in running into the harbour, in throwing a large quantity of provisions and a reinforcement of 10,000 men into the city, and in returning unmolested. The besieging land army was not much more fortunate. They began with a regular attack; machines were erected, and in a short time the batteries had demolished six of the towers flanking the walls, so that the breach soon appeared to be practicable. But the able Carthaginian commander Himilco parried this assault by giving orders for the erection of a second wall behind the breach. An attempt of the Romans to enter into an understanding with the garrison was likewise frustrated in proper time. And, after a first sally made for the purpose of burning the Roman set of machines had been repulsed, the Carthaginians succeeded during a stormy night in effecting their object. Upon this the Romans abandoned their preparations for an assault, and contented themselves with blockading the walls by land and water. The prospect of success in this way was indeed very remote, so long as they were unable wholly to preclude the entrance of the enemy's vessels; and the army of the besiegers was in a condition not much better than that of the besieged in the city, because their supplies were frequently cut off by the numerous and bold light cavalry of the Carthaginians, and their ranks began to be thinned by the diseases indigenous to that unwholesome region. The capture of Lilybaeum, however, was of sufficient importance to induce a patient perseverance in the laborious task, which promised to be crowned in time with the desired success.

But the new consul Publius Claudius considered the task of maintaining the investment of Lilybaeum too trifling: he preferred to change once more the plan of operations, and with his numerous newly-manned vessels suddenly to surprise the Carthaginian fleet which was waiting in the neighbouring harbour of Drepana. With the whole blockading squadron, which had taken on board volunteers from the legions, he started about midnight, and sailing in good order with his right wing by the shore, and his left in the open sea, he safely reached the harbour of Drepana at sunrise. Here the Phoenician admiral Atarbas was in command. Although surprised, he did not lose his presence of mind or allow himself to be shut up in the harbour, but as the Roman ships entered the harbour, which opens to the south in the form of a sickle, on the one side, he withdrew his vessels from it by the opposite side which was still free, and stationed them in line on the outside. No other course remained to the Roman admiral but to recall as speedily as possible the foremost vessels from the harbour, and to make his arrangements for battle in like manner in front of it; but in consequence of this retrograde movement he lost the free choice of his position, and was obliged to accept battle in a line, which on the one hand was outflanked by that of the enemy to the extent of five ships - for there was not time fully to deploy the vessels as they issued from the harbour - and on the other hand was crowded so close on the shore that his vessels could neither retreat, nor sail behind the line so as to come to each other's aid. Not only was the battle lost before it began, but the Roman fleet was so completely ensnared that it fell almost wholly into the hands of the enemy. The consul indeed escaped, for he was the first who fled; but 93 Roman vessels, more than three-fourths of the blockading fleet, with the flower of the Roman legions on board, fell into the hands of the Phoenicians. It was the first and only great naval victory which the Carthaginians gained over the Romans. Lilybaeum was practically relieved on the side towards the sea, for though the remains of the Roman fleet returned to their former position, they were now much too weak seriously to blockade a harbour which had never been wholly closed, and they could only protect themselves from the attack of the Carthaginian ships with the assistance of the land army. That single imprudent act of an inexperienced and criminally thoughtless officer had thrown away all that had been with so much difficulty attained by the long and galling warfare around the fortress; and those war-vessels of the Romans which his presumption had not forfeited were shortly afterwards destroyed by the folly of his colleague.

The second consul, Lucius Junius Pullus, who had received the charge of lading at Syracuse the supplies destined for the army at Lilybaeum, and of convoying the transports along the south coast of the island with a second Roman fleet of 120 war-vessels, instead of keeping his ships together, committed the error of allowing the first convoy to depart alone and of only following with the second. When the Carthaginian vice-admiral, Carthalo, who with a hundred select ships blockaded the Roman fleet in the port of Lilybaeum, received the intelligence, he proceeded to the south coast of the island, cut off the two Roman squadrons from each other by interposing between them, and compelled them to take shelter in two harbours of refuge on the inhospitable shores of Gela and Camarina. The attacks of the Carthaginians were indeed bravely repulsed by the Romans with the help of the shore batteries, which had for some time been erected there as everywhere along the coast; but, as the Romans could not hope to effect a junction and continue their voyage, Carthalo could leave the elements to finish his work. The next great storm, accordingly, completely annihilated the two Roman fleets in their wretched roadsteads, while the Phoenician admiral easily weathered it on the open sea with his unencumbered and well-managed ships. The Romans, however, succeeded in saving the greater part of the crews and cargoes (505).

The Roman senate was in perplexity. The war had now reached its sixteenth year; and they seemed to be farther from their object in the sixteenth than in the first. In this war four large fleets had perished, three of them with Roman armies on board; a fourth select land army had been destroyed by the enemy in Libya; to say nothing of the numerous losses which had been occasioned by the minor naval engagements, and by the battles, and still more by the outpost warfare and the diseases, of Sicily.

What a multitude of human lives the war swept away may be seen from the fact, that the burgess-roll merely from 502 to 507 decreased by about 40,000, a sixth part of the entire number; and this does not include the losses of the allies, who bore the whole brunt of the war by sea, and, in addition, at least an equal proportion with the Romans of the warfare by land. Of the financial loss it is not possible to form any conception; but both the direct damage sustained in ships and materiel, and the indirect injury through the paralyzing of trade, must have been enormous. An evil still greater than this was the exhaustion of all the methods by which they had sought to terminate the war. They had tried a landing in Africa with their forces fresh and in the full career of victory, and had totally failed. They had undertaken to storm Sicily town by town; the lesser places had fallen, but the two mighty naval strongholds of Lilybaeum and Drepana stood more invincible than ever. What were they to do? In fact, there was to some extent reason for despondency. The fathers of the city became faint-hearted; they allowed matters simply to take their course, knowing well that a war protracted without object or end was more pernicious for Italy than the straining of the last man and the last penny, but without that courage and confidence in the nation and in fortune, which could demand new sacrifices in addition to those that had already been lavished in vain. They dismissed the fleet; at the most they encouraged privateering, and with that view placed the war-vessels of the state at the disposal of captains who were ready to undertake a piratical warfare on their own account. The war by land was continued nominally, because they could not do otherwise; but they were content with observing the Sicilian fortresses and barely maintaining what they possessed, - measures which, in the absence of a fleet, required a very numerous army and extremely costly preparations.