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Editor’s Note: This is part of a new series of essays entitled “Battle Studies,” which seeks, through the study of military history, to demonstrate how past lessons about strategy, operations, and tactics apply to current defense challenges.

The Battle of Cannae, fought on Aug. 2, 216 BCE, the crowning success of Hannibal Barca over the Romans, sits comfortably in the pantheon of great military victories. It is one of the most spectacular examples of adroit tactics enabling a smaller, less heavily equipped army to defeat a larger, heavier opposing force in an open, pitched battle. However, though Cannae is frequently described as a “decisive victory,” it was, of course, nothing of the sort: The battle took place two years into the 17-year-long Second Punic War, which Hannibal lost. The failure of even the greatest of tactical victories to alter the overall strategic situation is every bit as much of the legacy of Cannae as Hannibal’s dazzling double-envelopment tactics.

Three accounts of the Battle of Cannae survive, none of them contemporary. The oldest is Polybius, writing in the mid-second century BCE. Polybius came to Rome in 167 and both interviewed surviving witnesses of the war and relied on the (now lost) history of Fabius Pictor, who had been a member of the Roman Senate at the time of the battle. The other essential source is the Roman historian Livy, writing at the end of the first century BCE. Livy relied on Fabius Pictor and Polybius, but also a number of other lost historical works, including that of Lucius Coelius Antipater, though his account is hampered by his own lack of military experience and a few embellishments born of literary pretensions. Finally, the second century CE historian Appian also provides an account of the battle, though it is confused and generally regarded to be of little value. Consequently, scholarly debates on Cannae remain focused on reconciling relatively small differences between Livy and Polybius’ accounts, which remain the bedrock of our understanding of the battle.

The Road to Cannae

The strategic situation Hannibal faced was rooted in the outcome of the First Punic War (264–241 BCE). In a real sense, the Second Punic War (218–201 BCE) was a continuation war. After a grinding war of exhaustion, the Romans had succeeded in 241 in conquering Sicily, ending more than two centuries of Carthaginian military activity on the island. Worse yet for Carthage, the combination of soldiers whose pay was long in arrears and the exhaustion of the treasury triggered nearly immediate major revolt of both its armies and its North African subjects in that same year. Hamilcar Barca emerged as Carthage’s preeminent general during the First Punic War and afterwards turned his armies toward expansion in Spain, perhaps seeking a resource base with which to match Rome. From 237 to 219, the Barcids (first Hamilcar, then his son-in-law Hasdrubal the Fair, then Hamilcar’s son Hannibal) expanded Carthaginian holdings in Spain, conquering all the Mediterranean coast south of the Ebro River, the people of which were known in antiquity as the Iberians, as distinct from other peoples living on the rest of the peninsula. This alarmed the Romans, who in 219 demanded Hannibal desist his attacks on the Iberian town of Saguntum, largely as a pretext for war. The Romans claimed that Hannibal’s assault was a breach of an agreement not to extend Carthaginian power north of the Ebro, despite Saguntum lying some 85 miles south of the river. Hannibal, now prepared to take on Rome, seized the town and began to move against Italy.

Hannibal’s strategy appears to have been to strike at the Roman alliance system in Italy. A little over half of Rome’s soldiers in this period were socii (“allies”), drawn from subordinated non-citizen communities of Italy, subdued by Rome either by conquest or diplomacy. These communities were required to send soldiers to serve in Roman armies in exchange for military protection and a share of the loot of future conquests. It was this system Hannibal aimed to disrupt, perhaps reasoning from Carthage’s own recent past in 241 where military exhaustion had produced a dangerous revolt among its own subject communities in North Africa. Consequently, Hannibal’s operations focused on despoiling allied territory in Italy to entice or compel the allies to defect. Such attacks would also draw Roman field armies, whose destruction Hannibal might have hoped would accelerate the collapse of the system.

Reaching Italy was no easy task. Roman naval superiority, hard-won in the First Punic War, mandated a treacherous overland march over the Pyrenees, through southern France (then Gaul) and over the Alps into what the Romans called Cisalpine Gaul, “Gaul on this side of the Alps,” a distance of roughly 1,000 miles. Polybius reports that Hannibal crossed the Pyrenees with 50,000 infantrymen and 9,000 cavalrymen, the majority of both drawn from Spain. By the time he descended from the Alps into Cisalpine Gaul, this force had been winnowed to merely 20,000 infantry and 6,000 cavalry. Hannibal could, however, count on the Gallic peoples of Cisalpine Gaul as allies if he could produce victories against Rome’s scrambling response to his arrival, which he did at Ticinus (218) and Trebia (218). The combination of casualties at Trebia and the harsh winter conditions (the battle was fought in December) cost Hannibal all but one of the elephants he had laboriously transported over the Alps. As a result, elephants would play no further role in his campaign in Italy. The following year, Hannibal raided Roman allies in Etruria (modern Tuscany), knowing that it would lure the Romans into another engagement. He sprung his ambush at Lake Trasimene (June 217), destroying yet another Roman field army.

The disaster at Trasimene in turn pushed Roman strategy into the political arena. In the immediate aftermath a complex political wrangle ensued that our sources allow us to observe only imperfectly. Eventually the Romans decided that a temporary supreme commander, a dictator, was required and Quintus Fabius Maximus was elected by the people. Fabius, soon nicknamed cunctator (“the delayer”), favored a strategy of containment against Hannibal, delaying him and avoiding a pitched battle while the Romans made gains where Hannibal wasn’t, raising fresh armies that could stabilize its alliances in Italy, and dismantling Carthage’s overseas holdings, particularly in Spain. Fabius shadowed Hannibal’s army into Campania and then Apulia in southern Italy, interfering with its logistics to contain Hannibal’s movements, but at Rome the politics remained unsettled.

The political issue came to a head as Fabius’ short term as dictator came to an end and elections were held for 216. The election of Gaius Terentius Varro and Lucius Aemilius Paullus (father of the victor at Pydna) as consuls resulted in a renewed strategy of confrontation. As the campaigning season began in the spring of 216, the Romans set out once again to try to defeat Hannibal in pitched battle. By this point, Hannibal had continued his southward movement, perhaps hoping to capitalize on anti-Roman sentiment farther south. He skirmished with the Roman army shadowing his movements through the late winter and spring of 216, before moving in late July against the Roman supply post at Cannae. Hannibal almost certainly aimed to draw the Romans into a battle on ground of his choosing, in this case a plain lying adjacent to the river Aufidus (the modern Ofanto) that offered ample room for his cavalry. The Roman army, under the joint command of both consuls, duly followed, setting the stage for the battle at Cannae.

Tactical Brilliance

Hannibal’s double envelopment at Cannae — involving simultaneous attacks on both flanks of the Roman formation ­— stands as one of the greatest tactical maneuvers in history, enabling his army to almost entirely destroy a far larger and more lavishly equipped Roman force.

The precise composition of both armies at Cannae remains somewhat uncertain, although the topline figures for both are relatively secure. On the Carthaginian side, Polybius reports Hannibal had by this point 40,000 infantrymen and 10,000 cavalrymen, but he did not specify the internal divisions of those figures. Working backwards through previous reports for Hannibal’s strength, it is possible to come up with a relatively narrow range of plausible breakdowns. John Lazenby offers an estimate that by this point Hannibal had perhaps 6,000 Iberian infantry and 10,000 African infantry left of his original force, which if we add the roughly 8,000 light missile troops Hannibal had at the Trebia, would leave 16,000 Gauls drawn from the rebellious territories of Cisalpine Gaul to make up the final infantry figure of 40,000 men.

The equipment of Hannibal’s force was diverse. A common translation error, rendering the light infantry lonchophoroi as “pikemen” instead of the more accurate “javelin men,” has left the lingering misconception that Carthage’s African infantry fought in a pike phalanx akin to the Macedonians, but in fact Carthage’s heavy infantry never used pikes and fought instead using shields with one-handed spears and swords, while the light infantry lonchophoroi fought with the lonche, a light spear that could double as a javelin. By 216, both Polybius and Livy note that Hannibal’s Africans had looted so much Roman equipment as to resemble Roman heavy infantry.

By contrast, both the Gauls and Iberians were clad in their own customary style: Gallic warriors fought mostly unarmored but with large oval shields, spears, and longer one-handed straight swords, while Iberian warriors fought with a mix of large oval and smaller circular shields, spears, and a dangerous forward-curved sword, the falcata. Far more lightly armored than Roman heavy infantry, both would have been at a disadvantage in a prolonged melee. Hannibal’s cavalry consisted of Gallic and Iberian cavalry, as well as Numidian horsemen. The Gauls and Spaniards represented heavier and lighter “shock” cavalry variants, respectively, while the Numidians fought as skirmishing light javelin cavalry and were considered the finest horsemen in the Western Mediterranean.

On the other side, the Roman army was substantially larger and more uniform. Polybius and Livy differ on whether the force consisted of either more legions or simply overstrength legions, but both come to similar total strengths, with roughly 80,000 infantrymen and 6,000 cavalrymen, split almost evenly between Roman citizens and socii, both of whom used the same equipment and tactics. The great strength of the Roman army was in its heavy infantry, formed in three successive battle lines, the triplex acies. The Romans aimed to overwhelm by infantry frontal assault, grinding down enemies with successive lines of heavy infantry while cavalry screened the flanks. And most Roman commanders, Fabius Maximus notwithstanding, seeking to notch a victory before their year in office expired, could be relied on to attack if given even a modest opportunity.

It was this predictable aggression and direct tactical approach that Hannibal would use against Varro and Paullus. He placed his lighter Iberian and Gallic infantry in the center, flanked by the heavier Africans. His Iberian and Gallic cavalry held the left flank and his Numidian cavalry the right. Rather than refuse his vulnerable center, Hannibal bent it forward, inviting the Romans to attack. The ensuing battle played out according to Hannibal’s plan: The Roman heavy infantry pushed his center back, advancing into the pocket created by the positioning of the African infantry on the flanks. The heavily armed Africans in turn pivoted and fell on the Roman flanks. Meanwhile, the Roman socii cavalry on Hannibal’s left was held at bay by the skirmishing Numidians, while the Iberian and Gallic cavalry overwhelmed the Roman citizen cavalry on the right. That accomplished, Hannibal’s cavalry officer, Hasdrubal (no relation to Hannibal’s brother, Hasdrubal Barca), moved part of his force to the left, scattering the remaining socii cavalry and, having completed the encirclement, charged the Roman infantry in the rear.

The slaughter in the center of the field was horrific. Engaged on all sides, the Roman infantry could no longer respond in a unified, effective fashion, but fought in a desperate, uncoordinated struggle within a steadily shrinking space. The Roman style of fighting required reasonably large intervals to be effective and the Romans must have ended up pressed so tightly together as to be unable to fight effectively. Livy provides terrible anecdotes of men found after the battle having suffocated themselves with heads buried in vain efforts to dig out of the horror, or wounded Carthaginian soldiers scratched and gnawed as Romans, no longer able to lift their weapons, had died gouging and biting in the press.

Image: Battle of Cannae (United States Military Academy Ancient and Medieval Warfare Atlas)

The Victory That Didn’t Matter

The virtual annihilation of a massive Roman force at Cannae constituted Hannibal’s greatest victory. Polybius reports 70,000 Roman dead and only 3,000 survivors but, as Lazenby notes, Polybius has left out a substantial camp guard, prisoners, and quite a few escaping soldiers from his tally of survivors. Livy’s casualty figures for the Romans are more reliable: 47,700 Roman soldiers killed, another 19,300 taken prisoner, and 14,550 escaped. But given the scale of the slaughter and completeness of Hannibal’s victory, the most shocking thing about the battle is that it wasn’t enough.

Hannibal has been faulted since antiquity for not doing more with his victory. Indeed, Livy reports a rebuke from one of his officers that, “You know how to win, Hannibal, but not how to use victory.” In practice, Hannibal had few options. A lightning march on Rome, often proposed, was hardly practical. Rome was a walled city that still had two legions to defend it and the logistics of a siege were impossible without first reducing many other walled towns in the vicinity. Hannibal generally avoided besieging large towns during his campaign in Italy and his army may not have brought much in the way of catapults and other siege equipment, though such specialized engines were hardly necessary for ancient sieges that tended to be more focused on earthworks than artillery. Far more importantly, Rome’s wide-reaching conscription and large alliance system left the Romans with tremendous military resources still available: The Romans would still have 110,000 men in the field in 215, rising to 185,000 by 212. A Carthaginian army settling down to besiege Rome would have been swiftly isolated and surrounded.

Instead, Hannibal sensibly moved to consolidate revolt among Rome’s socii in southern Italy. But the structure of the Roman alliance system proved difficult to break apart. On the one hand, the Roman offer of security for military support led many communities to partner with Rome. On the other hand, as Michael Fronda has noted, Roman control had frozen many local conflicts, such that the revolt of one community might lock in the loyalty of its neighbors, limiting the spread of Hannibal’s support.

Meanwhile, Rome recovered. Shifting back to the Fabian strategy of delaying Hannibal while focusing on other fronts, the Romans used logistical denial to bottle Hannibal up in southern Italy while other Roman armies, for Rome could support many, began mopping up the revolting socii and rolling back Carthaginian control in Spain. Carthage’s resources were almost as vast as Rome’s — the Carthaginians would field an astounding peak of some 165,000 men in 215 — but absent Hannibal’s generalship, confined as he was to southern Italy, the Romans tended to win the battles with their more heavily equipped forces. The last of Carthaginian rule in Spain collapsed in 206 and the Romans began preparations in 205 to invade North Africa in 204. The Carthaginians, facing defeat at home, recalled Hannibal to command the defense, leading to a decisive battle at Zama in 202, with the recalled Hannibal facing Publius Cornelius Scipio. Hannibal’s defeat there spelled the end of both the Second Punic War and Carthaginian imperial ambitions.

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The Warnings of Cannae

The Battle of Cannae, of course, serves as the dominant model for the effectiveness of double-envelopment tactics. Alfred Schlieffen famously wrote a treatise on the battle as head of the German General Staff, in turn reverently translated into English in 1931 by the U.S. Army: The influence on the envelopment concept in both the Schlieffen Plan and later German Bewegungskrieg is clear. Studies of the battle remain commonplace in officer education and military field manuals covering tactics as an example where envelopment was used to offset numerical disparity. With this, of course, equally comes a warning against Varro and Paullus’ ill-considered aggression, which allowed Hannibal to determine the time and place of the engagement and draw the Romans into battle on favorable terms.

However, Hannibal’s tactical victory at Cannae did not yield strategic success. The canonization of the battle thus risks lionizing flashy tactical success over achieving strategic objectives. Indeed, Hannibal’s bold operational plan that led to Cannae forced harsh strategic realities that would spell ruin for both Hannibal and Carthage. Roman control in Italy was the product of nearly three centuries of slow work that resisted unraveling. By contrast, the Barcid empire in Spain was barely two decades old and started to unravel almost immediately once the Carthaginians faced setbacks on the battlefield. Hannibal had correctly assessed that the Roman “center of gravity” was its reliance on the military resources of the socii, but the Barcid military system was equally reliant on Iberian manpower and even more vulnerable, as Roman victories in Spain could peel away Hannibal’s Iberian vassals even more readily than Hannibal’s victories in Italy had picked off Rome’s Italian allies.

As such, despite Hannibal’s spectacular tactical success, in the immediate aftermath of Cannae the overall balance of military power almost immediately began reasserting itself: The gap in resources between Rome and Carthage was simply too broad for even a talent like Hannibal to bridge. The Carthaginians would win further battles, particularly a crushing double victory on the Upper Baetis in 211 that halted, for a moment, the Roman advance in Spain, but they could not equalize the balance of power. Cannae thus also serves as a grim reminder of the supremacy of the strategic over the tactical and the difficulty of translating even the most tremendous tactical successes into new strategic realities.

Bret C. Devereaux is a teaching assistant professor at North Carolina State University and a historian whose research focuses on the intersection of the economy and military of the Roman Republic. He also writes a weekly history blog, A Collection of Unmitigated Pedantry (acoup.blog), and has an upcoming book, Of Arms and Men: Why Rome Always Won, a comparative study of mobilization and the costs of fielding armies in the Mediterranean during the third and second centuries BCE.

Image: Yale University Art Gallery via Wikimedia Commons