The immediate cause of the Second Punic War was the Saguntine affair, which Polybius prefers to regard as the first incident in, rather than a cause of, the war. The question at issue was whether by attacking Saguntum Hannibal violated any treaty with Rome.16Patriotic Roman annalists (e.g. Livy, xxi, 2, 7; Appian, Iber., 7) hastened to invent fictions to show that he had: for instance, they said that he broke the Ebro treaty by crossing the river to attack Saguntum, whereas the town lies a hundred miles south of the Ebro; or they suggest that a special clause was inserted in the Ebro treaty to the effect that Rome and Carthage should respect the neutrality of Saguntum. But it is not by such means that the blame can be assigned to Carthage.
There were two treaties which Hannibal’s action might have infringed: that of Lutatius in 241 and the Ebro convention of 226. Rome’s alliance with Saguntum was later than the treaty of Lutatius, so that the town was not included in the list of Rome’s allies whom the Carthaginians had promised to respect. The latter, therefore, were quite correct in insisting that Hannibal had not violated this treaty. But what of the Ebro agreement? Unfortunately, it cannot be related chronologically to Rome’s alliance with Saguntum with any degree of certainty; nor are its terms altogether clear. Even its validity has been questioned. It was a convention between Hasdrubal and delegates of the Roman Senate. It was probably ratified in Rome, and the Romans regarded it as legally binding on both parties, since the Carthaginians did not disavow their general who made it or his successor who, according to the Roman claim, transgressed it. The Carthaginians, however, denied that it had been ratified by their government. By its terms Hasdrubal renounced all hostile action north of the Ebro; his quid pro quo is not stated. Some suggest that he received little, others much. For instance, some allege that the treaty was unilateral and that as a member of a conquered nation Hasdrubal had to acquiesce in Rome’s wish; or on the other hand, others hold that the Ebro treaty defined the spheres of influence of the two nations and that it imposed on the Romans, either explicitly or implicitly, the obligation not to interfere south of the river. Probably, however, the concession made by Rome in face of the Gallic peril was to leave Hasdrubal free to extend his Spanish empire up to the river. How this affected Rome’s Saguntine alliance depends on the date assigned to the latter, which Polybius places ‘several years before the time of Hannibal’. If, as seems more probable, the alliance was prior to the treaty, it was then virtually annulled by the spirit of the new covenant, and could not in fairness be used by the Romans as a handle to check Punic expansion in the south. If Rome accepted the alliance after 226, she was deliberately interfering in an area where she had in effect recognized Carthaginian control. Whichever date, then, is correct, Rome had no legal ground to restrain Hannibal from attacking Saguntum; indeed she made no military attempt to do this. However unwise the Carthaginian general may have been, he was within his legal rights and was no treaty-breaker.17
But if Hannibal’s conscience was clear on the legal score, if he was merely returning the compliment for Rome’s interference with the Torboletae, he could not turn a blind eye to the political aspect. He was attacking a town which was under the declared protection of Rome, and he had been warned that its capture would be regarded as a casus belli. Yet he persisted – and from no military necessity. The frontier quarrel between the Saguntines and Torboletae need not involve hostilities, unless Hannibal wished. True, the acquisition of Saguntum would remove an awkward thorn from his side in the event of war with Rome; but its military value was not sufficient to warrant the risk of war. Nor had the Romans thrown a protective garrison into the town, as they had into Messana in 264; such an act would have violated treaty rights, which they were unwilling to disregard till the fall of the town made action imperative. Hannibal therefore persisted for other reasons; because he judged war with Rome was inevitable and because by manoeuvring the Romans into a false position he had forced on them the onus of declaring war, so that he could expect the continued support of his home government. (The view of Fabius Pictor, refuted by Polybius (iii, 8) that Hannibal did not have the backing of the Carthaginian government either at this time or during the war, should be rejected.) His capture of Saguntum may not have been the cause of war, but it undoubtedly caused the outbreak of war at that moment.
The immediate cause of war was thus the action of Hannibal and his government, but what were the underlying causes? Polybius finds three. First, the hatred of Hamilcar towards Rome; after his forced surrender in Sicily he lived for revenge and his spirit survived him. Secondly, the bitterness felt at Carthage when Rome seized Sardinia and renewed the threat of war. Thirdly, resulting from this, Hamilcar’s activity and the Carthaginian success in Spain.18 Did the Second Punic War then owe its origin to the hatred of the house of Barca; was it a war of revenge? The answer must depend on the interpretation given to the motives of the Barcids in Spain. Were they building up resources and an army with which to hurl themselves against Rome or were they merely trying to compensate their country for its loss of Sicily and Sardinia; was the object of their empire-building offensive or defensive?
Hamilcar had gone to Spain immediately after his country had been humiliated by Rome in 237; he cannot have forgotten his enforced capitulation in Sicily; and he made his son swear never to be friends with Rome. These facts establish beyond doubt his hatred of Rome, but they do not prove that he contemplated revenge or that he went to Spain to plan it. Rather, he went with the intention of re-establishing his country’s lost empire. He must have foreseen the possibility of renewed rivalry and he wanted to equip Carthage for the future, whatever that might hold. The fact that he did not rebuild a large Punic navy need not signify his pacific intentions (and anyway it would have been an unnecessary annoyance to Rome); it probably meant that in the event of war he planned to fight by land as Hannibal did when the day came. He wished to be prepared rather than to reopen the question. His successor Hasdrubal pursued still more clearly a defensive policy. When Rome was seriously engaged with the Gauls, so far from joining the attack on their side, he deliberately concluded a treaty with Rome which confined his activity to Spain. Hannibal, however, had to face somewhat different circumstances, for the Romans began to interfere in Saguntum. It is not likely that they acted with the desire of bringing a hornets’ nest about their ears. But when they were freed from the Gallic peril, they began to look askance at the growing Punic power in Spain which they themselves had sanctioned; doubtless Massilia brought the situation to their notice. Their action at Saguntum was little more than a gentle hint to Hannibal to walk warily, but it was enough to fan his smouldering wrath to a blaze. He determined to make it a test case to see whether Rome would abide by her treaty; but he must have foreseen the result. The Barcids had remained true to a defensive policy till they feared, whether with good cause or not, a repetition of the Sardinian question. And this time the Carthaginians refused to bow their necks.
Hannibal had cleverly precipitated a crisis in which the Romans were technically at fault, but from which they could not retreat without loss of prestige. He was thus immediately responsible for a war which neither Rome nor Carthage had deliberately engineered. Yet it was improbable that the two Republics could have lived at peace indefinitely. A balance of powers, such as existed in the Hellenistic east, might have been maintained for a time, yet causes of friction would inevitably occur now that Rome had been forced to become a world power. But throughout the years between the first two Punic wars Rome had not followed a deliberately aggressive policy. It has been suggested that there was strong disagreement in the state between an agrarian party under Flaminius, which limited its outlook to Italy, and a capitalistic party which favoured a Weltpolitik. While admitting a real clash of interests, it is unlikely that the latter party formed any deliberate imperialistic policy. The Senate rather met practical difficulties with practical solutions than followed a consistent and carefully conceived scheme.19 The seizure of Sardinia, which was the aggressive act of a nervous bully, represented a passing mood. The Gallic wars were defensive in spirit, though they caused Rome to safeguard her northern frontier. Her early action in Spain was due more to the apprehension of her ally, Massilia, than to a studied western policy. The intervention in Illyria was a necessary piece of police work. True, all these acts involved future responsibility. Once she had set her hand to the plough there could be no turning back. But Rome could hardly be expected to anticipate the ultimate result of each action. She dealt with each situation as it arose and if Hannibal chose to challenge her interference in Spain, she was willing to face the consequences and to determine the lordship of the western Mediterranean.