Later, incursions—invariably from east to west—remained both rare and sporadic, failing to kindle any sustained engagement. Athens’s Sicilian expedition (415−412 BCE) proved a disaster. Interventions by rulers of Sparta (342–338 BCE) and Epirus (334–331 BCE) in southern Italy on behalf of local Greek communities likewise ended in failure, and a more scattershot Spartan mercenary venture (303–302 BCE) was similarly unsuccessful. Pyrrhus of Epirus was unable to score more than Pyrrhic victories in Italy and Sicily (280–275 BCE). Farther south, the Macedonian general Ophellas’s ill-fated march into Carthaginian territory to support a Greek Sicilian assault failed to expand the eastern PMN into the Maghreb. None of these failures were preordained: nor was the death of Alexander the Great at the tender age of thirty-three just as he had begun to turn his gaze toward the western Mediterranean, a highly contingent event I consider in chapter 4.
Effectively unencumbered by the ancient network that had grown out of the Fertile Crescent region, a smaller and separate western Mediterranean PMN eventually emerged along a north-south axis of conflict from Italy through Sicily to Tunisia (figure 3.2). It was rooted in intensifying hostility between Carthage and Syracuse (off and on from 410 BCE following an early clash in 480 BCE) and then between Rome and Carthage (264–241 and 218–201 BCE) and between Rome and Syracuse (264–263 and 215–212 BCE).
Roman military operations on the Adriatic east coast (229–228 and 220–219 BCE) were the first to cross the divide from the other direction, a harbinger of the storm to come. After inconclusive conflict with Macedon (214–205 BCE) as a sideshow of the Hannibalic War, it was Rome’s subsequent invasion of Macedon (200–197 BCE) and its response to the Seleucid advance into Greece (192–190 BCE) that fully merged the western and eastern PMNs.
FIGURE 3.2 Political-military networks in the ancient Mediterranean during the third quarter of the first millennium BCE.
Rome did not enter what had initially been a very limited Carthaginian-Sicilian network until its control over peninsular had been consolidated, and crossed over into the much larger eastern PMN only after its principal rivals in the western Mediterranean—Syracuse and Carthage—had been neutralized. Rome consequently remained shielded from serious challenges by more complex polities while it was still in the process of scaling up its co-optation and mobilization strategy to maturity. I explore the contingent nature of this outcome in chapter 4 by asking how much would have to have been different for this process to be derailed.
THE SOUTHERN PERIPHERY
Once Rome had established hegemony over the entire Italian peninsula by the 260s BCE, further advances were to bring it in close contact with societies that were rather differently organized, and in many cases the more differently, the more distant they were.
Both the Greek polities in Sicily and the Carthaginian empire in North Africa shared certain characteristics with the Roman-Italian state and alliance system. The Greek or Hellenized populations were organized in city-states and had a long tradition of popular military participation. Compared to Rome, Syracuse, the principal Sicilian power, had followed a more capital-intensive path of state formation, most notably through its aggressive employment of mercenaries. However, a significant coercive dimension was also present.3
Much the same was true of Carthage, which had erected a multilayer power structure not unlike Rome’s, made up of a privileged metropolitan center, closely connected allied cities of shared Punic ethnicity, indigenous subjects in the interior, and more peripheral allies and partners. Carthage relied on a combination of capital- and coercion-intensive strategies, the former embodied by its strong navy and recourse to mercenaries, the latter by exploitation of its rural hinterland.4
The greatest differences lay in the sphere of military capabilities. Sicily supported a much smaller population than peninsular Italy, and it appears that the island’s military forces never exceeded 30,000–40,000 men. Attempts to build a Greater Syracusan state beyond Sicily by reaching into south Italy and North Africa had foundered on Carthaginian resistance coupled with recurrent internal instability.5
Thanks to its extensive continental hinterland and access to the coastal regions of the westernmost Mediterranean, Carthage was better positioned to pursue open-ended expansion. At the time of its major conflicts with Rome, its overall population base may have been roughly comparable to that of its opponent, and it was also able to recruit widely outside the Maghreb. The Carthaginian elite was imbued with a strong militaristic ethos, and military participation in the metropolitan core was high. Mobilization rates could reach Roman levels at least in emergencies, as citizens alternately staffed a fleet of up to 200 warships or fielded armies of anywhere from 20,000 to 40,000.6
Scale was a major constraint: because this strong mobilization capacity did not extend in equal measure to its subjects and allies, the surrounding layers of subordinates produced either levies at lower per capita rates or tribute to fund relatively expensive mercenaries. Indigenous military forces played an important role but were not very large relative to the source population. As a result, Carthage could either raise a large army or launch a powerful fleet, but not both at the same time. When faced with Rome’s superior manpower, it increasingly drew on external mercenaries. Constrained by the size of its metropole, it lacked Rome’s ability to replace lost citizen troops on a large scale.7
Moreover, Carthaginian control even of its immediate hinterland in northern Tunisia was fragile: based on military and tributary obligations without obvious rewards, it was vulnerable to defection whenever the occupying power’s military fortunes waned. Carthage consequently lagged behind Rome in both demographic depth and organizational resilience. Its ventures in Sicily had been checked by the Sicilian Greeks, and systematic exploitation of the resources of the Iberian peninsula appears to have been a fairly late development.8
Even so, within these constraints, Carthage enjoyed considerable success in scaling up its efforts in wartime. We may question whether it could actually deploy more than 200 warships with some 60,000 crew, even if our main source for its first war with Rome credits Carthage with 350 ships for almost 150,000 men. But there is little doubt that in the second war, Carthage maintained up to 100,000 soldiers spread out across several different theaters.9
These commitments help explain why Carthage managed to challenge Rome for a prolonged period of time. Pushed by the latter to expand its military resources on an unprecedented scale, Carthage was ultimately unable to match or dismantle the mass mobilization system of the Italian peninsula. Once again, albeit delayed by Carthage’s—most famously Hannibal’s—intermittent tactical battlefield superiority, Rome’s structural advantages proved too strong to overcome.
THE EASTERN PERIPHERY
To the east, the southeastern tip of Italy was not far away from Greek city-states and other groups that had merged into larger federal entities (koina). Endowed with considerable military resources—the ancient tradition of citizen levies and military training of young men continued in many Greek polities, even as recourse to mercenaries had become common—compared to Roman Italy, even the largest federations were severely constrained in manpower. The Aetolian league in northwestern Greece that initially sided with and then opposed Rome never fielded more than 15,000 soldiers and probably not even that many in any one place. Other major players in Greece were unlikely to marshal much larger forces.10
Most of the eastern Mediterranean was dominated by three Hellenistic kingdoms, successor states to the ephemeral empire of Alexander the Great. Their field armies were built around fixed formations of heavy infantry coupled with cavalry and, on occasion, war elephants. Core forces of professional soldiers and mercenaries could be supplemented by ethnic levies.11
Fortuitously, the kingdom closest to Italy, Macedon, was only the smallest. The principal source of manpower for Alexander’s far-reaching campaigns, it had been drained of fighting men at exactly the same time as Rome was establishing its hegemony over peninsular
Italy. Although Macedon rebuilt its military system in the third century BCE by combining local levies with hired mercenaries, it was never able to field more than 30,000–40,000 soldiers, and its naval assets remained fairly modest. Moreover, Macedon was enmeshed in and constrained by a competitive state system in the southern Balkans and Aegean that was fertile ground for opportunistic alliances and balancing as Rome advanced into this region.12
The two larger and more capable kingdoms were located farther away from Italy: the Seleucid empire stretched from Asia Minor to eastern Iran, and that of the Ptolemies covered Egypt, the Cyrenaica, and parts of the eastern Mediterranean and south Anatolian coastlands. Each of them could put together an army of 70,000 to 80,000, on a par with the largest Roman levies, yet without a comparable depth in reserves. Shaped by their origin as foreign conquest regimes, these two powers heavily relied on a limited number of professional soldiers but generally sought to avoid large-scale conscription among the diverse subject populations they ruled and taxed.
And while the Ptolemaic navy of 300 ships with up to 80,000 men in part of the third century BCE compares well with Roman naval forces at the peak of the First Punic War, the Ptolemaic state, separated from Italy by shared enemies real and potential, was never a hostile power. It is also unclear whether it could have replaced losses on the same enormous scale as the Romans did when they fought Carthage. The Seleucids neglected to build up significant naval resources until the beginning of the second century BCE, and even then never mustered more than 100 major warships, small fry compared to Roman sea power since the First Punic War.13
While all these specifics favored Rome, they are only part of a larger story of even more lopsided Roman political and military superiority. First of all, the Hellenistic world was thoroughly divided. By the time Rome entered the eastern Mediterranean, the major powers had been locked into unceasing conflict and shifting alliances for more than a century. Between 274 and 101 BCE, the Seleucid and Ptolemaic kingdoms were to fight no fewer than nine wars for control of their Levantine borderlands, known as the Syrian Wars. Although these conflicts spurred on state formation and honed military capabilities on both sides, it was a zero-sum game, interspersed with a periodic near-collapse of one party or the other.14
More specifically, when Rome first attacked Macedon in earnest from 200 to 197 BCE, the Seleucid and Ptolemaic states were embroiled in their fifth war. Although there is no good reason to believe that greater coordination among these kingdoms would have sufficed to block Rome’s advance, this illustrates the pernicious consequences of their mutual antagonism: I discuss in chapter 4 the deliberately far-fetched scenario of a unified Macedonian empire on the scale of Alexander’s and the odds of its withstanding Roman imperialism.15
Second, the well-trained Hellenistic field armies were precious in that they could not readily be replaced. The Seleucid and Ptolemaic empires each relied on core units of approximately 36,000 heavy infantry and cavalry augmented by some 15,000 mercenaries. Whereas the Seleucid state might have been able to replace half its core units within a reasonable amount of time, Ptolemaic reserves were even more constricted: in an emergency, Ptolemy IV had to train 20,000 of his Egyptian subjects to fight Macedonian style, a measure that risked undermining the ruler’s own position as the head of a foreign conquest regime.16
The Seleucid and Ptolemaic “cleruchs” (military settlers) who formed the backbone of these core units were irreplaceable in the short term: their number, largely determined by the availability of crown land, imposed an effective limit on army strength. In the third century BCE, this manpower base stabilized just as Rome’s kept expanding. The overall supply of suitably skilled external mercenaries was likewise inelastic. Additional forces would have had to be raised from subjects and allies of diverse background and reliability, an option that was both cumbersome and politically undesirable.17
All of this was a far cry from the high degree of homogeneity and coordination on the Roman side. As already noted, from 200 to 168 BCE, Rome fielded an average of 120,000 soldiers each year, ranging from a minimum of 75,000—equivalent to the largest armies ever amassed by Seleucids or Ptolemies—to a maximum of 180,000, well beyond its opponents’ capacity. And even that was only the tip of the iceberg: whereas Rome could at least in theory fall back on 750,000 or more potential recruits, and had on an earlier occasion (in the 210s BCE) called up close to one in three of them after suffering over 100,000 fatalities, nothing even remotely similar would have been feasible for any of the Hellenistic states.18
The dramatic extent of this imbalance is thrown into sharp relief by the fact that Rome was able to prosecute several wars against major Hellenistic powers without having to put anything like the full weight of its military behind these efforts (figure 3.3). Thus, only about a quarter of the Roman and allied soldiers mobilized at the time were deployed in two wars with Macedon, and even the much larger Seleucid empire could be dealt with by a little less than half of Rome’s overall levy. In the same vein, Rome never dispatched more than a little over 100 warships to these theaters, a small fraction of its commitment in its first war against Carthage. In a nutshell, the Romans were able to defeat Alexander’s heirs with one arm tied behind their backs.19
FIGURE 3.3 Roman troop deployments by region as a share of all deployments, 200–168 BCE.
Third, Hellenistic armies were much more expensive in per capita terms than the forces of the Romans and their Italian allies. Even allowing for wide margins of uncertainty, we may estimate that in nominal terms, a Seleucid or Ptolemaic infantryman cost anywhere from three to six times as much per day as the average soldier on the Roman side.20
There were two main reasons for this enormous gap: nominal prices and wages were higher in the economically more developed Hellenistic world than in Italy, and professional soldiers and mercenaries commanded wages that were much higher than those of Roman and allied soldiers not merely in nominal terms but also in real ones. Thus, while the Hellenistic powers struggled to channel vast financial resources into their voracious militaries, the more nimble Roman state relied on large numbers of low-cost conscripts and enjoyed the added advantage of recruitment below actual cost among its Italian allies, an arrangement sustained by allied self-funding and the promise of booty.21
None of this might have mattered much if the professional forces of the Hellenistic kings had offset their high price with superior performance on the battlefield. However, and this is the fourth and final point, after Roman intervention in the eastern Mediterranean gathered momentum in 200 BCE, the Hellenistic armies arrayed against them lost every single major engagement—the Macedonians at Cynoscephalae (197) and again at Pydna (168) and the Seleucids at Thermopylae (191) and Magnesia (190). The same was true of every pitched naval encounter. Even if actual casualty figures need not have been as lopsided as biased Roman sources made them out to be, this dismal record speaks for itself. Tactical superiority on the battlefield thus compounded Rome’s strategic advantage in manpower and funding.22
In this context, the contingencies inherent in the outcome of battles are of little relevance: even if Rome had lost some or even all of these engagements, it could easily have deployed fresh military resources—just as it had done in its previous wars with Carthage—whereas its opponents were unable to do the same. When Seleucid and Ptolemaic commanders subsequently reorganized and equipped some of their infantry in the Roman style, these reforms failed to address the underlying structural causes of Roman military superiority: its ability to draw cheaply and deeply on a thoroughly militarized population numbering in the millions. We can now see that the later Roman historian Livy did not exaggerate when he wrote that the Romans had won these wars “not only without defeat but even without danger to themselves.”23
This pattern continued during the first century BCE as Rome advanced farther east. In a series of conflicts from the 80s to the 40s BCE, the armies of the more distant Hellenistic powers of Pontus (in northeastern Anatolia) and
Armenia were consistently defeated in every battle in which the Roman side fielded more than 10,000 men from Italy. It took the unfamiliar cavalry tactics of the Iranian Parthians (who had by then taken over much of the Seleucid empire) in 53 BCE to finally destroy a more substantial Roman army in difficult terrain—and even that episode did not detract from Rome’s overall strategic advantage along its eastern frontier for the next 300 years.24
In the early second century BCE, the playing field could hardly have been more slanted in Rome’s favor. The Hellenistic kingdoms were not only hamstrung by smaller effective forces, a lack of manpower reserves, and much higher costs, they also lost all the time. These factors make Roman success appear so overdetermined that it would be difficult to come up with any plausible counterfactuals to produce significantly different outcomes. From this perspective, the internal integrity of its opponents hardly counts as a decisive factor. But even in this sphere, the stable Roman commonwealth enjoyed a striking advantage. The Seleucid dynasty had only temporarily overcome a period of fission to fight the Romans and subsequently suffered from growing internal destabilization and growing pressure from the Iranian Parthians as they rolled up their empire from the rear. The Ptolemies likewise experienced serious domestic conflicts and before long ended up under Roman protection to shield their Egyptian heartland from Seleucid encroachment (168 BCE).
THE NORTHERN AND WESTERN PERIPHERY
I found it necessary to go into some detail to show why Rome had little difficulty overcoming seemingly powerful imperial competitors in the most developed part of western Eurasia. Most of its European periphery can be dealt with much more briefly. To the north and west, Rome faced a stateless periphery of chiefdoms and tribes. While the small-scale entities may well have boasted high military participation rates, they were—with rare and fleeting exceptions—too fragmented to pool their resources in an effective manner. This greatly reduced the risk of invasion or rival state formation.25
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