The hard-won victory over the mercenaries earned the Carthaginians only a brief respite from their troubles. In Sardinia, their last significant overseas possession, a mercenary rebellion every bit as brutal as the African insurrection had broken out in 240 BC. After the rebels killed Bostar, the military governor on the island, and other Carthaginians, a force was dispatched from Carthage. After arriving, however, its mercenary troops mutinied and crucified their Carthaginian general, then massacred all the Carthaginians in Sardinia.38
What made the situation even more precarious was that there seems to have been some coordination between the two revolts. Polybius recounts how a letter from the Sardinian mutineers was sent to the African rebels which appeared to impart information about persons in their camp who were secretly negotiating with the Carthaginians.39 Although Polybius believes that the letter could have been a fabrication, it is possible that the mercenary troops sent out from Carthage to Sardinia may have had some knowledge of this. Alarmingly for Carthage, in 240 the mercenaries offered to hand over the island to Rome. For the time being the Romans declined this invitation, and without powerful allies the mercenaries were soon driven off the island by indigenous Sardinians. Taking refuge in Italy, they once more approached the Romans to aid their enterprise, and this time their offer was accepted.
In 238 BC Rome let it be known that it was planning an expedition to occupy Sardinia. When the Carthaginians quite justifiably objected –on the grounds that the 241 treaty recognized their sovereignty over the island–and then stated their intention to retake it, the Romans declared that they would consider this a declaration of war. Severely weakened after years of conflict, Carthage had to back down. In 237 both Sardinia and the neighbouring island of Corsica were seized, and matters were made even worse by the Roman demand of a further indemnity of 1,200 talents from Carthage.40
Even Polybius strongly condemned the Roman annexation of Sardinia, which was in his words ‘contrary to all justice’ and an action for which ‘it is impossible to discover any reasonable pretext or cause.’41 These were sharp criticisms from one of Rome’s strongest supporters. Why did Rome, after initially turning down the inducements of the rebels, eventually break its own treaty and take Sardinia for itself? Later writers, perhaps buying into Roman propaganda of the time, argued that this was retaliation for Carthage’s imprisonment, and in some cases execution, of the Italian traders who were caught profiteering from the Mercenaries’ Revolt.42 This seems highly implausible given the earlier amicable agreement between the two powers. The answer very probably lies in the aggressive and acquisitive behaviour that had been the hallmark of Roman foreign policy for some time, and there were a number of reasons why the Romans had now taken up an invitation that they had first refused in 240.43
Carthage had in 238 defeated the rebels in North Africa and could now turn its full attention to reclaiming Sardinia (indeed, a further force was being prepared under the command of Hamilcar Barca for that purpose).44 Rome, therefore, annexed the island to prevent Carthage from reasserting itself in the central Mediterranean.45 It should also be noted that it was the Roman Popular Assembly–a body which had already proved itself willing to take a far more hawkish attitude towards Carthage–that voted for the annexation of Sardinia.46 The fact that the mercenaries had massacred the Carthaginians on the island before being driven out also made it easier for the Romans to present this as a simple occupation of neutral territory.47
The annexation of Sardinia had a seismic impact on future events. Economically, Sardinia had been a very important part of the Carthaginian zone of influence. As the Carthaginian hold on western Sicily had become increasingly insecure, Sardinian mints had increasingly taken on the production of Carthage’s bronze coinage.48 The loss of Sardinia was a blow not merely to Carthage’s economic prospects, however, but also to its sense of pride. Rome’s annexation of the territory and demand for indemnities were a brutal reminder that Carthage’s former status as a major player in the central Mediterranean, disingenuously acknowledged in the 241 treaty just a few years before, was no more.