The Ghosts of Cannae: Hannibal and the Darkest Hour of the Roman Republic

by Robert L. O'Connell

  Tiberius Sempronius Longus and his consular army were now back in Italy. Livy (21.51.6–7) has them sailing from Sicily to Ariminum (modern Rimini) high on the Adriatic side of the Italian boot, but it would have been dangerously late in the season for such an extended voyage. More probable is Polybius’s (3.68.9–14) version of them marching to the same destination along the Via Flaminia, reaching this point in early December. On the way, the historian reports, they passed through Rome, where the consensus was that the skirmish at the Ticinus constituted but a minor setback. Infantry, not cavalry, mattered, and that Sempronius’s army—presumably more capable than Scipio’s—had to do little more than show up to decide the showdown with the Carthaginians.

  So, brimming with confidence, Sempronius reached the River Trebia in mid-December and settled his men down next to Scipio’s secure camp. He found his colleague still nursing his wound and generally depressed about the prospects of successfully engaging the Punic army. Scipio argued that the winter months were best spent training what remained of his mostly inexperienced force, while this period of inaction would also cause the mercurial Gauls to begin drifting away from Hannibal. Some have maintained that this reasoning was a later invention designed to protect the Scipionic reputation,12 but it was also very good advice.

  Sempronius would have none of it. He was, after all, a Roman, and one whose consulship’s hourglass was quickly running down. Likely his every instinct told him (as Scipio’s had earlier) to aggressively seek glory in battle as quickly as possible. Hannibal almost immediately provided the pretext.

  Some of the local allied Gauls were apparently two-timing him, hedging their bets and keeping channels open to the Romans. Hannibal knew this was dangerous and unacceptable, and sent out several thousand Celts and Numidians to ravage their territory between the Trebia and the Po. The Gauls in turn appealed to the Romans for help. Sempronius jumped at the opportunity, deploying his own cavalry and about a thousand velites to deal with the raiders. They caught the Punic marauders scattered and weighed down with booty, and sent them racing pell-mell to the Carthaginian camp. Realizing what had happened, the Carthaginian commanders of the outposts sent a covering force forward, which in turn chased the Romans back to their encampment. This tit-for-tat action took on a momentum of its own, with both sides feeding reinforcements until all the Roman velites and cavalry were engaged and the fighting ebbed and flowed uncontrollably across a wide area. Just as it threatened to escalate into a full-scale battle, Hannibal called a halt. Polybius (3.69.12–13) tells us because the Punic commander knew a “decisive engagement should never be undertaken on any chance pretext and without definite purpose.” Yet it is likely that Hannibal called a halt not because the tit-for-tat action had no “definite purpose” but because the halt itself had a purpose of its own. He was, to use the modern idiom, “preparing the battlefield,” specifically that portion that lay between the opposing commander’s ears.

  Sempronius was elated by his apparent success, especially since it had been accomplished by the very parts of the force that had been defeated under Scipio. Despite his colleague’s continued warnings against rash action, Sempronius made up his mind to seek a decisive engagement as soon as opportunity knocked—exactly what Hannibal, short on supplies and long on fickle Gauls, wanted. Livy (21.53.7–11) tells us he had been briefed on Sempronius’s impulsiveness, and he now set about building a battle around it.

  The opposing camps were separated by the River Trebia, a shallow braided watercourse swollen by winter rains. On Hannibal’s side beyond the west bank was a broad, flat, treeless plain ideal for cavalry, but it was also the kind of terrain favored by Roman infantry—in other words, the obvious site of battle. Studying the ground to the south, Hannibal discovered a streambed overgrown with vegetation ideal for hiding ambushers. The night before the date he intended to fight, Hannibal secretly sent his brother Mago and a mixed force of two thousand Numidians into this position, with orders to hit the Romans from the rear at the appropriate moment.

  At dawn, beneath brooding skies and a cold driving snowfall, the bait was set. Hannibal sent the Numidian cavalry across the river with orders to harass the Roman outposts and lure them and whoever would follow back across the Trebia. Sempronius, playing the human equivalent of Pavlov’s dog, responded exactly as expected, sending all four thousand of his cavalry and six thousand velites after the Numidians, and ordering his heavy infantry to muster immediately and march out of camp without even having their breakfast. This force, sixteen thousand Romans and twenty thousand allied—basically two consular armies13—dutifully waded chest deep across the ice-cold Trebia, marched onto the plain beyond, and deployed for battle in the standard pattern, Romans in the center and allies on the wings—a process likely to have consumed several frigid sleet-laced hours.14 Hungry, wet, and cold—even for soldiers as tough as Romans, this was not a good way to start a battle.

  While the Numidians ran the Roman cavalry and velites into exhaustion, Hannibal ordered eight thousand light infantry forward to support them and act as a screen. Only then—after his men had eaten their fill, had armed and rubbed themselves down with oil in front of their campfires—did he lead them out onto the field of battle. He was probably outnumbered, but not decisively so, his army having been swelled by around fourteen thousand Celts.15 He had a clear advantage in cavalry, both in numbers and quality. His infantry formed a single line, Africans and Spaniards to the right and left, with the Gauls in the center, where their individual size and ferocity might blunt the forward surge of the Roman legionaries, hopefully until the other Punic force components could seize the advantage. The Spanish and Gallic cavalry were placed on the flanks, where they were joined by the Numidian horse, back from harassing the Romans, a body of five thousand on either wing … and, it appears, the elephants, probably half-frozen and almost useless. It was time to fight.

  The battle opened with the Punic cavalry bearing down on the Roman horsemen, who were now stationed in two groups of two thousand on the flanks of the allied infantry. They didn’t stay long; exhausted and outnumbered, they were routed and scattered by a combination of Punic cavalry and a cloud of javelins thrown by the Carthaginian light troops, who had moved back to their own wings. The Punic cavalry and light infantry now began enveloping both ends of the long Roman line, swarming the allied heavy infantry from all directions and beginning to roll it up.

  The fight went better for the Romans in the center. The hastati and principes seemed to have absorbed the initial shock of the individual Gallic swordsmen and were methodically grinding through them, and some of the African units, when Mago and his Numidians emerged from hiding to hit the Roman line in the rear. The Romans’ forward momentum slowed as the triarii turned to face this threat. The younger Barcid’s timing was fortuitous; if the core body of Romans had broken through the Punic forces quickly, they might have had the opportunity to part in the middle and pivot back to support the flagging allied flanks. Instead, Mago managed to throw the entire line into confusion,16 and soon after, both alae and the adjacent Roman units disintegrated into useless human blobs.

  Ten thousand legionaries in the middle, though, maintained their formations and finally broke through the Punic line. But with no flanks left to defend and only Carthaginians and the ice-cold Trebia to the rear, they kept marching right off the battlefield and made their way to Placentia and safety. For most of their trapped compatriots, however, death was the only refuge. While there are no casualty figures,17 most men likely fell prey to Carthaginians, drowning, or simply exposure.

  Almost certainly the tempo of battle was progressively determined by hypothermia. As the day wore on, the snow turned to a cold penetrating rain that must have sucked the vitality from all the combatants. At least the Carthaginians had been acclimatized in the Alps; many of their adversaries had been basking in the warmth of Sicily not much more than a month earlier. Livy (21.54.9) refers to the Romans after crossing the Trebia as scarcely able to hold their arms, a
nd growing progressively weaker as the day wore on. Because Hannibal had made sure that the Carthaginians had eaten breakfast and otherwise prepared themselves, they must have had a body heat advantage at the beginning, but Livy (21.56) makes it clear that they grew increasingly benumbed. At the end, the fighting and even the slaughter must have taken place in stiff-limbed slow motion, with no attempt made to cross the river and take the Roman encampment. Instead, the Carthaginians staggered back to their own camp, and stayed there, cold and passive for the next several days, a period during which many of their pack animals and almost all of the elephants succumbed to exposure.18 This hypothermic lassitude probably saved Scipio and the Romans left to guard the camp; they were able to escape by rafting down the Trebia, and eventually joined the other fugitives at Placentia.

  It appears19 that Sempronius tried to disguise the magnitude of his defeat, sending messengers to Rome to announce that a battle had taken place and that only the storm had deprived him of victory. Quickly his countrymen learned the truth—Hannibal and his army remained secure in their camp, virtually all the Gauls had gone over to him, and fragments of two consular armies were scattered in various localities, cut off from supply except by the River Po. The situation was obviously serious, but the first steps taken to shore up Rome’s position seem pointed in the wrong direction. The Romans readied a fleet of sixty quinqueremes and reinforced Sardinia and Sicily, as if the main threat would come from Carthage and not Hannibal. Still apparently trying to salvage his reputation, Sempronius, Livy (21.57.3–4) tells us, boldly made his way to Rome to preside over the consular elections. The results there also reflected a sense of emergency, though not necessarily good choices. Joining C. Servilius Geminus as consular colleague was Caius Flaminius, the Gauls’ archenemy and, because he’d provided them with Gallic land he’d conquered, the Roman farmers’ friend. He was definitely a controversial figure, particularly among the wealthier elements of the nobility, but his career was all about pummeling the Gauls, and he was known to be a man of action. One can almost hear the conventional wisdom along the Tiber: “Flaminius is just the man to take care of this problem up north.” But he had yet to meet Hannibal.

  The ancient Greeks had a term, aristeia, for a serial display of heroic excellence—a sort of berserker kill-fest in which a central character hacks down any and all who stand in his way—in The Iliad, for instance, when Achilles single-handedly routs the Trojan army. The term seems appropriate for Hannibal; such was the magnitude and audacity of his initial series of victories over the Romans. Trebia marked the beginning of the series, and Cannae the climax. But in the first contest he had already revealed the qualities that would make him one of the greatest soldiers who ever lived—his X-ray vision into the minds of his opponents, his trickiness and penchant for surprise, his judicious use of his men, both in their care and feeding and also in how he applied each force component to maximum advantage.20 (The only significant Carthaginian casualties were the Celts who had been placed in the center to absorb the brunt of the Roman assault—troops of uncertain loyalty, virtually untrained, and easily replaceable at this point.) It was a virtuoso display, but unfortunately for the Romans, Hannibal was far from satisfied.

  For in the winter of 218–17 his position and that of his army were far from secure. Food must have been a constant concern. Livy (21.57–8) speaks of several Punic attacks on supply depots near Placentia, and a failed attempt to cross the Apennines to find better foraging. Modern historians21 often dismiss these accounts as inventions, but these stories certainly speak to a very basic preoccupation in an environment where Gallic agriculture likely did not produce significant surpluses.

  This may have been reflected in Hannibal’s treatment of his prisoners. The Roman captives, whom he expected to ransom, he fed only enough to keep them alive. The Roman allies in his hands he treated better, and after a time he gathered them together, informing them that his war was against Rome and for the liberty of Italy’s people.22 With this he freed them all without ransom. This is generally seen as the first step in Hannibal’s political and information campaign to undermine Rome’s alliance structure, and it undoubtedly was. But it is also worth mentioning that it left him with hundreds, perhaps thousands, fewer mouths to feed.

  His precarious status and the questionable hospitality of his hosts were further evidenced in the tale Polybius and Livy both tell of Hannibal having to wear various disguises, even different-colored wigs, to avoid assassination at the hands of the locals.23 The Gauls had not rallied to the Punic standard in order to find their own territory as the seat of war and the kitchen table for what amounted to an occupying army. If Hannibal wanted to keep the Gauls as allies, he had better move south as soon as the weather turned.

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  Springtime for Hannibal meant winter for Etruria and Rome.24 Actually, there were two ways he could have gone. The Apennines form the spine of Italy, dividing it longitudinally. Therefore, he could have marched east toward the Adriatic side and then headed south, where he was likely to find support among those most recently conquered by Rome. This route also would have brought him closer to Carthage. Alternatively, he had the choice of moving down to the passes of the Apennines and heading west into Etruria, leaving open communications with the Po valley and Spain, and also putting himself in a position much more directly threatening to Rome itself. Given his motives and his true base of support in Iberia, he chose the latter.

  Knowing their own geography, the Romans hedged their bets. They sent Geminus north along the Via Flaminia (the same route probably taken by Sempronius) to Ariminum, where he could combine his new recruits with Publius Scipio’s veterans25 and cover the eastern corridor down the peninsula. Flaminius had already arrived at this destination, assuming office here and not in Rome, thereby flouting tradition and skipping the religious rituals normally presided over by an incoming consul. To compound matters, he ignored the commissioners sent to recall him. Instead, he added the remnants of Sempronius’s force to his own legionaries and moved to Arretium, where he thought he would be in a position to block the Apennine passes leading toward Etruria.26

  He wasn’t. Hannibal gave him the slip crossing at the Porretta pass,27 and then struck out through the flooded marshes surrounding the River Arno. This was not simply a matter of deception; as usual the Punic commander had a hidden agenda. The march also would serve as a means of toughening the Gauls and weeding out the weak ones. This trek would be a swampy version of the one over the Alps. He lined up his army with the Spaniards and Africans intermingled with the baggage train, the Celts sandwiched in the middle, and Mago and the Numidians to the rear to keep the whole mass moving and the Gauls from turning back. Those who survived slogged continuously for three days and nights. They had to; in this inundated terrain there was no place above water to rest except upon the corpses of the many fallen pack animals. Cavalry horses frequently lost their hoofs. Hannibal, atop the last surviving elephant, contracted a case of ophthalmia so severe that he lost the sight of one eye.28 All told, it was a bad trip. But when the Carthaginians emerged from the morass somewhere around Faesulae (modern Fiesole), the army was not only clear of the Romans, but also it had rid itself of fair-weather Gauls and begun the process of fully integrating the remaining Gauls into the force structure.

  Hannibal’s swarm of scouts and spies had been busy. They confirmed that the rich Etrurian plain was ripe for the plucking and that Flaminius, still at Arretium, was a commander every bit as impulsive and belligerent as Sempronius and just as easy to trap. Hannibal decided to lead him on a fool’s errand south. And as he traveled he understood exactly how to distract the Roman commander; nothing would infuriate the farmers’ friend more than Hannibal’s foragers’ descending like a plague of locusts onto the villages and fields of Rome’s allies. Here in the heart of Italy, Flaminius had only to follow the smoke columns to follow Hannibal, a humiliating circumstance that could be stopped only by bringing Hannibal into action, which Flaminius was determined to
do.

  Both Polybius and Livy maintain that Flaminius was discouraged by his subordinates, who advised him to await reinforcement from Geminus.29 He ignored them, and also in typical Flaminius fashion, he overlooked a series of ill omens (here is where the hard-to-pull-up tent standards came into play), and probably did so appropriately, if only because he was a Roman and was predisposed to fight. Besides, Hannibal was on the move; how could his colleague Geminus have been expected to catch up? It also says something that Flaminius’s army was joined by a host of irregulars carrying chains for the prisoners they expected to take and enslave after an easy victory. So Flaminius, as always with his ear more attuned to vox populi than to the council of prudence, went forward in hot pursuit.

  No more than a day ahead, Hannibal came upon Lake Trasimene and saw opportunity along the route before him—a narrow plain that separated the shoreline from a parallel track of steep hills, the entrance to which was a blind defile. He slowed his army so that late in the day Flaminius would march up and see him entering the gulch, and later Flaminius’s scouts would observe the Punic campgrounds near the far end of the line of hills. The Romans settled down for the night outside the gulch entrance. Hannibal, under the cover of darkness, led his forces back down a parallel path on the other side of the hills and stationed the men high along the hills’ reverse slopes, awaiting the arrival of dawn.