This section deals with how successfully the Rome's alliance with the
socii withstood the military challenges it faced in the two and a half centuries of its existence (338–88 BC). The challenges may be divided into three broad periods: (1) 338 to 281 BC, when the confederation was tested mainly by challenges from other Italian powers, especially the Samnites; (2) 281 to 201 BC, when the main threat to the confederation was intervention in Italy by non-Italian powers i.e. Pyrrhus' invasion (281 to 275 BC) and Hannibal's invasion (218 to 203 BC); (3) 201 to 90 BC when the
socii were called upon to support the Rome's imperialist expansion outside Italy. Elements of all three phases overlap: for example, Gallic invasions of the peninsula from the North recurred throughout the period.
Samnite Wars Phase I (338–281 BC) was dominated by the three
Samnite Wars, the result of which was the subjugation of the Romans' main military rival on the peninsula, the
Samnite league. The loyalty of the then
socii during this period appears to have remained largely solid. There were sporadic revolts: in 315, 306, 269, and 264 BC by some Campanian cities, the
Aurunci,
Hernici, and
Piceni, respectively. But these were isolated cases and never turned into a general revolt of the
socii. Most importantly, when in 297–3 Rome faced its gravest threat in this period, a coalition of Samnites and Gauls, the
socii of the time did not abandon Rome. At the
Battle of Sentinum (295), where a huge combined army of Samnites and Gauls suffered a crushing defeat, the
socii contingents actually outnumbered the 18,000 Romans (4 legions deployed).
Pyrrhic War Phase II (281–203 BC) saw even greater trials of the confederation's cohesion by external invaders with large and sophisticated armies. The intervention in southern Italy of the Epirote king
Pyrrhus (281–275 BC), with 25,000 troops, brought the Romans into conflict with a Hellenistic professional army for the first time. Pyrrhus had been invited by Tarentum, which had been alarmed by Roman encroachment in Lucania. The arrival of Pyrrhus triggered a widespread revolt by the southern
socii, the Samnites, Lucani and Bruttii. But the revolt was far from universal. The Campanians and Apulians largely remained loyal to Rome. This was probably due to their long-standing antagonism to the Samnites and Tarentines respectively. Neapolis, the key Greek city on the Tyrrhenian, also refused to join Pyrrhus, due to its rivalry with Tarentum. This demonstrates a critical element in the success of Rome's military confederation: the
socii were so divided by mutual antagonisms, often regarding their neighbours as far greater threats than the Romans, that they were never able to stage a universal revolt. The pattern is similar to that of the next great foreign challenge, Hannibal's invasion of Italy (see below). The central Italians (Etruscans and Umbrians) remained loyal, while the southern Italians, with significant exceptions, rebelled. The exceptions were also the similar, save for the Campanians, who joined Hannibal in the later episode. In the event, the Roman forces surprised Pyrrhus by proving a good match for his own, which was unexpected, given that the Romans were temporary levies pitted against professionals. The Romans won one major battle (
Beneventum) and lost two (
Heraclea and
Asculum), although in these they inflicted such heavy casualties on the enemy that the term "Pyrrhic victory" was coined. The defeat at Beneventum forced Pyrrhus to withdraw in 275, but it was not until 272 that the rebel
socii were reduced. The surviving accounts for this later phase of the war are thin, but its scale is clear from Rome's celebration of 10
triumphs, each implying the slaughter of at least 5,000 enemy.
Second Punic War The loose federation's gravest trial came with the Second Punic War and Hannibal's invasion of Italy (218–201 BC). This was not only because the Romans suffered a string of devastating defeats, but also because Hannibal's entire war strategy was to break up the confederation by inducing the
socii to rebel against Rome's hegemony and join a counter-alliance under Hannibal's overall command. In the event, he had only mixed success: • Of the Roman citizens
sine suffragio (which were mainly Italic tribes wholly annexed to the Roman state) Hannibal scored one major success: the defection of most of the Campanians. This was the most surprising of the defections, as the Campanians had been loyal allies of Rome since the 340's BC, when they requested Roman protection from Samnite incursions. They had also remained loyal during the Pyrrhic invasion, as Pyrrhus was the champion of the Campanians' other main rivals, the Italiote Greeks. The deciding factor in Capua's defection from Rome appears to have been the prospect of replacing Rome as Italy's leading city. • Not a single Latin colony defected to Hannibal, despite the latter's policy of treating the Latin colonists in the same way as other
socii: i.e. releasing captured Latin soldiers without ransom and sparing the colonies' territory from devastation. The closest any Latin colonies came to mutiny was in 209 BC (after eight years of war), when 12 colonies sent a delegation to Rome to inform the Senate that they had run out of men and money and could supply no more troops. But even this was not a defection to the enemy, but an attempt to pressure the Senate into making peace. The inhabitants of the colonies were descendants of Romans and original Latins and were bound to Rome by ethnic solidarity (although they had nominally lost their citizenship, they could automatically regain it by moving to Roman territory). In addition, the colonists occupied land seized from the neighbouring Italic tribes, which the latter were keen to regain. They therefore had little to gain and everything to lose by joining Hannibal's Italic coalition. (None even joined the Italian coalition in the
Social War over a century later, when there was no external threat). • Of Rome's Italian
socii, Hannibal largely failed to win over the central Italians. The Etruscans and the Umbrian-speaking tribes (Marsi, Marrucini, Paeligni and Frentani) remained loyal. In the later years of the war, the Romans suspected some Etruscan city-states of plotting treachery and took limited military precautions, but no substantial revolt ever materialised. Etruscan ancestral fear of Hannibal's Gallic allies was probably the decisive factor, plus intense rivalry between individual city-states. The central Italians' loyalty to Rome was a critical strategic obstruction to Hannibal, as it reinforced the belt of Roman territory through central Italy that cut off his southern alliance from his Gallic allies in the Po valley, preventing the latter from sending him reinforcements. The adherence of much of southern Italy gave Hannibal a relatively stable power-base that sustained his military presence in Italy for 13 years after Cannae. The Samnites, Bruttii and Lucani were, as demonstrated above, the biggest losers in Rome's territorial expansion. Of the Greek cities of the
Ionian Sea, Tarentum would certainly have defected immediately after Cannae if it hadn't been under the control of a Roman garrison, placed there in 218 BC to prevent precisely such an event. The Tarentines eventually succeeded in allowing in Hannibal's army in 212, although the Romans continued to hold the
citadel, which reduced the value of the gain for Hannibal. Thurii, Heraclea, Metapontum, Locri and Croton did defect after Cannae. The Greek cities on the
Tyrrhenian Sea — Rhegium and Neapolis — also refused to defect and remained staunchly loyal to Rome after Cannae. The Neapolitans had an intense rivalry with the Campanians, while the Rhegians had long struggled for survival against Hannibal's Bruttian allies. Also, for both cities, Tarentine hegemony was anathema. Neapolis was the main seaport of Campania, which in turn was the principal theatre of war. Rhegium controlled one shore of the
Strait of Messina and thus hindered Hannibal's communications with Carthaginian forces in Sicily. For these reasons, Hannibal's failure to take these two strategic ports greatly complicated the reinforcement and resupply of his army from Africa. Finally, all four of the major Samnite tribes, refused to join their minor compatriots' revolt. But by necessity, rather than from ideological conviction, the Carthaginians backed the anti-Roman democratic factions. Tarentum (212 BC) was delivered to Hannibal by the local democratic faction. (After the war, Hannibal himself supported democratic reform at Carthage, but whether he would have done so had Carthage won the war cannot be determined). Using the military manpower figures given in the table above, the Italian forces available to Hannibal can be estimated. Assuming that two-thirds of the Lucani and Bruttii and one-third of the Apulians and little under one third of Campanians and a fifth of the Samnites were on his side, they had zero complete Greeks and the total rebel Italian manpower was c. 150,000 men, to which must be added Hannibal's own Carthaginian army and Gallic allies. In contrast, the Romans could draw upon c. 650,000 Romans and Allies of undisputed loyalty. Of these, at 50,000 perished in Rome's great military disasters of 218–206 BC. The remaining 600,000 were roughly six times the maximum manpower Hannibal had in Italy. But in reality, Hannibal's position was even weaker than this. Rome's Italian confederates were organised in the regular structures of the military confederation under unified Roman command. Hannibal's Italian allies, on the other hand, served in their own units and under independent command. Only the Lucani are recorded as having joined Hannibal in operations outside their own territory. The rest were solely concerned with defending their own territory against Roman counter-attacks and were unwilling to join Hannibal's operations elsewhere. Each consular army-equivalent of c. 20,000 was probably as large as Hannibal's entire "mobile" army of Carthaginians and Gauls. This massive standing force proved an insurmountable obstacle for Hannibal. The multiple Roman armies could attack Hannibal's allies at several points simultaneously, while his own mobile army (Carthaginians and Gauls) was not large enough to intervene in more than a couple of theatres at once. In addition, his mobile army's supply lines were constantly threatened along their whole length, severely restricting its operational range. All the while, Hannibal faced a slow but inexorable shrinkage of his mobile army as he was unable to fully replace his campaign losses. Reinforcements by land from the North, whether of Gauls or other Carthaginians from Spain, were successfully blocked by the Romans, most importantly when they defeated Hannibal's brother
Hasdrubal's relief army at the
Battle of the Metaurus (207 BC). Reinforcements by sea were severely restricted by Roman sea power (although some reinforcements did get through by sea). For these reasons, Hannibal proved unable to prevent the Romans from reducing his Italian allied city-states one by one, despite his continuing success in virtually all battlefield encounters. Nevertheless, the Hannibalic War stretched Roman military manpower to the limit. Of their 400,000 available manpower, the Romans kept at least 200,000 men in the field, in Italy and overseas, continuously in the period 214–203 (and 240,000 in the peak year). In addition, c. 30,000 were serving in the Roman fleets at the same time. Thus, if one assumes that fresh recruits reaching military age were cancelled out by campaign losses, about 60% of the confederation's available manpower was under arms continuously. This barely left enough to tend the fields and produce the food supply. Even then, emergency measures were often needed to find enough recruits. Livy implies that, after Cannae, the minimum property qualification for legionary service was largely ignored. In addition, the normal ban on criminals, debtors and slaves serving in the legions was lifted. Twice the wealthy class were forced to contribute their slaves to man the fleets and twice boys under military age were enlisted. ==Course of the war==