Hannibal resolved immediately after his nomination (in the spring of 534) to commence the war. The land of the Celts was still in a ferment, and a war seemed imminent between Rome and Macedonia: he had good reason now to throw off the mask without delay and to carry the war whithersoever he pleased, before the Romans began it at their own convenience with a descent on Africa. His army was soon ready to take the field, and his exchequer was filled by some razzias on a great scale; but the Carthaginian government showed itself far from desirous of despatching the declaration of war to Rome. The place of Hasdrubal, the patriotic national leader, was even more difficult to fill in Carthage than that of Hasdrubal the general in Spain; the peace party had now the ascendency at home, and persecuted the leaders of the war party with political indictments. The rulers who had already cut down and mutilated the plans of Hamilcar were by no means inclined to allow the unknown young man, who now commanded in Spain, to vent his youthful patriotism at the expense of the state; and Hannibal hesitated personally to declare war in open opposition to the legitimate authorities. He tried to provoke the Saguntines to break the peace; but they contented themselves with making a complaint to Rome. Then, when a commission from Rome appeared, he tried to drive it to a declaration of war by treating it rudely; but the commissioners saw how matters stood: they kept silence in Spain, with a view to lodge complaints at Carthage and to report at home that Hannibal was ready to strike and that war was imminent. Thus the time passed away; accounts had already come of the death of Antigonus Doson, who had suddenly died nearly at the same time with Hasdrubal; in Cisalpine Gaul the establishment of fortresses was carried on by the Romans with redoubled rapidity and energy; preparations were made in Rome for putting a speedy end in the course of the next spring to the insurrection in Illyria. Every day was precious; Hannibal formed his resolution. He sent summary intimation to Carthage that the Saguntines were making aggressions on the Torboletes, subjects of Carthage, and he must therefore attack them; and without waiting for a reply he began in the spring of 535 the siege of a town which was in alliance with Rome, or, in other words, war against Rome. We may form some idea of the views and counsels that would prevail in Carthage from the impression produced in certain circles by York's capitulation. All "respectable men", it was said, disapproved an attack made "without orders"; there was talk of disavowal, of surrendering the daring officer. But whether it was that dread of the army and of the multitude nearer home outweighed in the Carthaginian council the fear of Rome; or that they perceived the impossibility of retracing such a step once taken; or that the mere vis inertiae prevented any definite action, they resolved at length to resolve on nothing and, if not to wage war, to let it nevertheless be waged. Saguntum defended itself, as only Spanish towns know how to conduct defence: had the Romans showed but a tithe of the energy of their clients, and not trifled away their time during the eight months' siege of Saguntum in the paltry warfare with Illyrian brigands, they might, masters as they were of the sea and of places suitable for landing, have spared themselves the disgrace of failing to grant the protection which they had promised, and might perhaps have given a different turn to the war. But they delayed, and the town was at length taken by storm. When Hannibal sent the spoil for distribution to Carthage, patriotism and zeal for war were roused in the hearts of many who had hitherto felt nothing of the kind, and the distribution cut off all prospect of coming to terms with Rome. Accordingly, when after the destruction of Saguntum a Roman embassy appeared at Carthage and demanded the surrender of the general and of the gerusiasts present in the camp, and when the Roman spokesman, interrupting an attempt at justification, broke off the discussion and, gathering up his robe, declared that he held in it peace and war and that the gerusia might choose between them, the gerusiasts mustered courage to reply that they left it to the choice of the Roman; and when he offered war, they accepted it (in the spring of 536).
Hannibal, who had lost a whole year through the obstinate resistance of the Saguntines, had as usual retired for the winter of 535-6 to Cartagena, to make all his preparations on the one hand for the attack of Italy, on the other for the defence of Spain and Africa; for, as he, like his father and his brother-in-law, held the supreme command in both countries, it devolved upon him to take measures also for the protection of his native land. The whole mass of his forces amounted to about 120,000 infantry and 16,000 cavalry; he had also 58 elephants, 32 quinqueremes manned, and 18 not manned, besides the elephants and vessels remaining at the capital. Excepting a few Ligurians among the light troops, there were no mercenaries in this Carthaginian army; the troops, with the exception of some Phoenician squadrons, consisted mainly of the Carthaginian subjects called out for service - Libyans and Spaniards. To insure the fidelity of the latter the general, who knew the men with whom he had to deal, gave them as a proof of his confidence a general leave of absence for the whole winter; while, not sharing the narrow-minded exclusiveness of Phoenician patriotism, he promised to the Libyans on his oath the citizenship of Carthage, should they return to Africa victorious. This mass of troops however was only destined in part for the expedition to Italy. Some 20,000 men were sent to Africa, the smaller portion of them proceeding to the capital and the Phoenician territory proper, the majority to the western point of Africa. For the protection of Spain 12,000 infantry, 2500 cavalry, and nearly the half of the elephants were left behind, in addition to the fleet stationed there; the chief command and the government of Spain were entrusted to Hannibal's younger brother Hasdrubal. The immediate territory of Carthage was comparatively weakly garrisoned, because the capital afforded in case of need sufficient resources; in like manner a moderate number of infantry sufficed for the present in Spain, where new levies could be procured with ease, whereas a comparatively large proportion of the arms specially African - horses and elephants - was retained there. The chief care was bestowed in securing the communications between Spain and Africa: with that view the fleet remained in Spain, and western Africa was guarded by a very strong body of troops. The fidelity of the troops was secured not only by hostages collected from the Spanish communities and detained in the stronghold of Saguntum, but by the removal of the soldiers from the districts where they were raised to other quarters: the east African militia were moved chiefly to Spain, the Spanish to Western Africa, the West African to Carthage. Adequate provision was thus made for defence. As to offensive measures, a squadron of 20 quinqueremes with 1000 soldiers on board was to sail from Carthage for the west coast of Italy and to pillage it, and a second of 25 sail was, if possible, to re-establish itself at Lilybaeum; Hannibal believed that he might count upon the government making this moderate amount of exertion. With the main army he determined in person to invade Italy; as was beyond doubt part of the original plan of Hamilcar. A decisive attack on Rome was only possible in Italy, as a similar attack on Carthage was only possible in Libya; as certainly as Rome meant to begin her next campaign with the latter, so certainly ought Carthage not to confine herself at the outset either to any secondary object of operations, such as Sicily, or to mere defence - defeat would in any case involve equal destruction, but victory would not yield equal fruit.