The early treaties between Rome and Carthage were treaties of friendship and for trade, formed to limit their spheres of influence. But in 306 the two Republics may have formed a closer political agreement which debarred the Carthaginians from interfering in Italy, and the Romans in Sicily (p. 124). Carthage again negotiated with Rome in 279; no defensive alliance was struck, but an emergency measure was designed, chiefly to keep Pyrrhus in Italy (p. 130). During the war Carthage neither received nor asked for help, not wishing to bring Romans into Sicily; Rome also kept to herself.
In 272 a puzzling incident occurred. When the Romans were besieging Tarentum, which was still held by Pyrrhus’ lieutenant Milo, a Carthaginian fleet suddenly appeared in the harbour, but quickly sailed off again. Had it come in reply to an appeal from Milo or on its own initiative; to help the Romans or to capture Tarentum? Later Roman writers accused Carthage of having tried to seize Tarentum, alleging that the action was a breach of treaty rights; but the Carthaginians had not tried to land. Indeed, far from acting contrary to the agreements, the Punic admiral may have sailed up in accordance with Mago’s treaty to see whether he could help the Romans. It is perhaps most likely that the Carthaginians were reconnoitring on the offchance of turning the situation to their advantage, but when this seemed impossible they sailed away, while the home government disavowed the admiral’s action and Rome accepted the apology, as recorded by Orosius. But whether Rome suspected treachery or merely rebuffed a friendly gesture, the result would hardly improve relations between the two Republics.8
When Pyrrhus left the shores of Sicily he is reported to have remarked: ‘What a cockpit we are now leaving for Carthaginian and Roman to fight in.’ The recent history of the island justified this prophecy. The Punic expansion had been checked during the reign of Agathocles as King of Syracuse (304–289), but after his death the Carthaginians again advanced their standards, until driven back by Pyrrhus. When he retired to Italy they defeated the Syracusan fleet, recovered their lost possessions and captured the Greek cities of central Sicily. Thus by 275 Syracuse’s influence was confined to eastern Sicily, and even there she met with rivals. Certain of Agathocles’ discharged Italian mercenaries on their return home had treacherously seized the town of Messana (c. 288). Styling themselves Mamertines, after the Sabellian war god Mamers, they settled there and proceeded to plunder the surrounding districts, Carthaginian and Greek alike. Defeated but not exterminated by Pyrrhus, they were later defeated by the Syracusans under Hiero who now, if not earlier, assumed the title of king (265–264) and then undertook the siege of Messana. At this point the Carthaginians intervened, refusing to look on while Syracuse won control of the Sicilian straits by capturing Messana. Their admiral threw a Punic garrison into the town with the consent of the Mamertines, and Hiero was obliged to return to Syracuse, disregarding the complimentary exhortations of the poet Theocritus to continue fighting. But the Mamertines did not wish to keep their new garrison indefinitely: some advocated reaching an agreement with Carthage by which their autonomy would be respected, others preferred to seek alliance with a less alien people, the Romans. The latter party prevailed and Rome was suddenly faced with a request for alliance and help. What was she to do?
Rome and Carthage were thus brought abruptly face to face. By ejecting from Rhegium the Campanians who had tried to play at pirates like the Mamertines in Sicily the Romans had won control of the Straits (270). But now a Carthaginian garrison at Messana faced them from the opposite shore: it barred their access to Sicily, and constituted a point d’appui from which, following the example set by Dionysius and Agathocles, the Carthaginians could sail against the towns of the Italian coast, once they had taken easternSicily. There could be no doubt that they would extend to Sicily the monopoly which they exercised throughout the western Mediterranean. That might not be of direct concern to the Romans, who were little interested in foreign trade, but it would be a severe blow to their allies in southern Italy. And there was the further danger that if Rome neglected her new Greek allies, they might turn to Carthage for protection in a desperate effort to preserve their Sicilian trade. It did indeed seem that Rome would have to listen to the appeal of the Mamertines, even though this might involve crossing swords with Carthage and possibly a deadly duel.
But the swords which the Mamertines virtually thrust into the rivals’ hands could scarcely have been kept permanently sheathed. Rome and Carthage had little in common. Different in race, culture and religion, with divergent moral and material interests, they would gravitate towards conflict when once the minor states between them had been eliminated or assimilated. In the Hellenistic east a common culture held the three great monarchies in a precarious balance of powers. When Rome had absorbed something of that culture, she adapted her policy in order to try to maintain the balance. But in the west rivalry would lead to war: compromise was difficult, if not impossible.
The immediate question before the Roman Senate was the appeal of the Mamertines, not war with Carthage, though the more far-sighted must have seen that this would probably follow the granting of the request. When the Senate failed to reach a decision the question was referred (by Appius Claudius?) to the people, who voted to send help to the Mamertines. Polybius, who here follows Fabius Pictor and thus gives at least a pro-Roman account, if not a tendentious justification, explains that the Senate hesitated, in spite of a full recognition of the danger of the advance of Carthage, because it felt unable to ally itself to a robber-state, especially as it had recently executed the brigands at Rhegium. But the weight of this moralistic argument has been questioned, since the seizure of Messana by the Mamertines had occurred twenty-five years earlier and the new state was now standing on its own feet and had been recognized by Carthage and several Greek cities; it was presumably autonomous and therefore Rome would not break her fetial law by granting alliance. Further, the parallel with Rhegium is weak, for there Rome interfered on behalf of her own allies, whereas she had had no dealings with Messana. But even if conscientious scruples were among the motives of the Senate’s hesitation, others also must be found in the fear of war with a great sea power, and in the aversion of the conservative element in the Senate to an expansionist policy which increased the power of the people and of the popular leaders whom a new war might bring into prominence. A further reason was probably that Roman interference in Sicily would involve a definite breach of the treaty of 306. The popular leaders who wanted war might argue that the Carthaginians had themselves annulled this agreement by theiraction at Tarentum, and by their general attitude which was, according to Polybius (i, 7), one motive that had stimulated Rhegium to ask Rome for protection (c. 280). But the Senate perhaps hesitated to disregard formal obligations.9
The people had accepted the Mamertine alliance because of the advantages which their leaders said would attend it. These suggested benefits would not be land, tribute, or even booty, but the checking of the advance of Carthage and the increase of allies with the consequent decrease of effort by the citizen army. The personal advantages to the popular leaders from success in war was an aspect which they would hardly emphasize, but of which such families as the Otacilii of Beneventum and the Campanian Atilii would be fully conscious. But the main motive which led Rome to accept the alliance of the Mamertines was to secure an outpost which was necessary to the safety of Italy. The two rivals may both have rushed to secure this key position, but their motives were different; defensive imperialism dominated Rome’s policy, an exploiting commercial imperialism actuated Carthage.