Things had grown rapidly worse since the building of the walled camp across the isthmus. Nothing could now be brought into the besieged city by land. The sea was still partly open. The Roman fleet kept up a blockade, but it was not really effective. As soon as the wind began to blow from the sea the war-ships had to stand off from the shore, and the blockade-runners had their opportunity. Prices ruled so high in the city that a trader who contrived to take safely to its destination one cargo out of two made a very handsome profit.
All the fishing population of the African coast for a hundred miles on either side of the besieged city was busily employed in the traffic. Light vessels drawing but little water were chiefly used, for they could be safely navigated in places where a war-ship would inevitably have grounded. So rudely and cheaply were they built that the loss, if they were wrecked, was insignificant. The great difficulty was the weather; if this continued to be fine for ten days together, a large part of the besieged population came within an easily measurable distance of starvation.
Scipio now resolved on making a great counter-move—he would block up the approach to the harbour. He had, in fact, for some time past foreseen the necessity of taking this step, and had prepared a vast amount of material for the work, employing great numbers of the native population in quarrying stone and cutting timber. So much had been accomplished in this way that when the time came for executing the work little more than the actual construction remained to be done. This was not so difficult as it had seemed. The harbour mouth was not very far from the shore occupied by the Romans.
The first thing was to lay a foundation for the mole that it was proposed to build. This was done by sinking huge blocks of roughly-hewn stone, chiefly during moonless nights. During this stage of the work the besieged took little heed of what was going on, or, anyhow, took no pains to interrupt or hinder it. There was a suspicion, and more than a suspicion, of Scipio's purpose, but Hasdrubal, himself indolent and incompetent, haughtily refused to listen to any suggestion from his subordinates. But even Hasdrubal was roused when the structure reached the surface of the water. What he saw was a mole, more than thirty yards broad, stretching across the mouth of the harbour, and shutting off every channel available even for the smallest craft.
Hasdrubal now developed, or accepted, a plan which for a time at least was a virtual check to Scipio's move. He kept up a brisk discharge of missiles on the men employed in building the mole. So sharp and continuous was it that the besiegers had little attention to give to what was being done on the opposite side of the harbour. It was a surprise, and a very unwelcome surprise to them, that no sooner had they stopped up one mouth of the harbour, than they found that another exit had been created. The whole population, every man, woman, and child in the city, that could ply a spade or a pick, wheel a barrow-load or carry a basket of earth, had been working night and day at excavating another mouth to the harbour.
Nor was this all; a still greater surprise, so great, indeed, as to be almost overwhelming, remained behind.
One of the conditions of the peace granted to Carthage after the fatal defeat of Zama[37] had been the surrender of all the ships of war but twenty. In a way this condition had been observed. There had never been more than twenty ships in commission at one time; but the old hulks had not always been destroyed. At first they had been kept to serve various purposes; latterly, as another war began to loom in the future, they had been preserved with the intention of using them again. A number of merchant vessels also were furnished with crews and an armament that was at least passably effective.
And, marvellous to relate, all this had been done without the knowledge of the besiegers. There was a constant flow of deserters from the city, increasing as time went on and the prospects of Carthage became less and less hopeful. Yet none of them had any definite information to give. That something was going on they knew; they had heard for some time a great sound of hammering—that, indeed, had been audible in the Roman camp when the wind blew from the dockyard—but the restrictions on admission to the arsenals had been rigidly enforced. So there ended the information which they were able to give.
Nothing, then, could have exceeded the astonishment of the besiegers when a new fleet, the existence of which no one had suspected, issued from a harbour mouth which no one had ever seen. A thin bank of earth had been kept to the last, so that to observers from outside, as also to the Roman ships as they cruised backwards and forwards along the coast, nothing appeared to have been changed. When everything else was ready, all the available labour in Carthage was set to work to clear this bank away. The task was finished by dawn. At sunrise the new fleet, magnificently equipped, for there had been a lavish expenditure on the ornament as well as the armament of the ships, sailed out of the harbour by its new exit.
Unfortunately for Carthage there was no one to make the most of the opportunity. A vigorous attack on the Roman fleet—scattered as it was, and altogether unprepared for action, some of the ships being under repair, and nearly all of them but half-manned, their crews being largely employed on shore—might have been successful, and have even postponed the fate of Carthage. But it was not to be. Hasdrubal, self-opinionated and incapable, paralysed everything and everybody. The fleet paraded for a while along the coast, and had the barren honour of holding without dispute, for that day at least, the possession of the sea.