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

by Robert L. O'Connell

  The Roman battle plan at Cannae can be summarized in three words: “pack the middle.” Because this approach would play into Hannibal’s own scheme and lead to a great disaster, it is easy to dismiss the plan as nonsensical. It wasn’t. Rather, it had a clear purpose, to maximize the Roman numerical advantage in infantry while minimizing the obvious Carthaginian superiority in cavalry. It was also based on past experience. At Trebia, ten thousand legionaries had finally managed to hack their way through the center of the Punic line, and had they been able to do it sooner, they could have split and pivoted to crush the Carthaginians attacking on each flank. Even amidst the surprise and demoralization of Trasimene the impetus of around six thousand Romans had carried them through the Carthaginian stopper force, only to be captured later. We can assume that Varro and Paullus and those advising them were confident in the ability of their troops to puncture the heart of the Punic line, and were intent on doing this as rapidly as possible. Geometrically this called for a narrow, thick formation, exactly the configuration on the day of the battle described by Polybius (3.113.3), “placing the maniples closer together than was formerly the usage and making the depth of each many times exceed its front.”

  Breaking though in this manner was decidedly not a matter of simple momentum, like some gigantic rugby scrum pushing inexorably forward. Romans fought primarily with short swords, so the cutting edge was by definition the first line of combatants. True, pila could be launched from several rows back, but any soldier behind around line eight would probably have hit a fellow Roman up front.

  The real arguments for this type of human geometry had to do with order, endurance, and psychology. Long narrow columns are easier to keep together, and, they therefore move faster and more cohesively on the battlefield.30 The many lines to the rear also insured an almost inexhaustible supply of fresh fighters to take the place of the fallen and exhausted, a kind of conveyor belt of shark’s teeth. Finally, a great many of the Roman participants at Cannae lacked combat experience; the middle of such a formation was a safe, psychologically reassuring place for them. One source equates this to the human instinct to herd together for mutual comfort, but without considering that this was actually prey behavior.31 The thickened manipular order could be expected to have massive combat endurance, which would make the formation almost impossible to defeat by frontal attack, and would thereby allow the unit to move steadily forward. But what would happen if it faced the unexpected, was hit from an unanticipated direction? At this point herding behavior might become just that, dissolving the maniples into a crowd compressed to the point of mass helplessness. The legions would lose the ability to replace frontline fighters through now nonexistent gaps between units. It was a prospect not pleasant to contemplate, and one we can be pretty sure the Romans failed to consider.

  Hannibal may have. Just how much he knew of the Romans’ plans prior to battle is impossible to say. Though Livy (22.41.5–6) maintains that “all the circumstances of his enemies were as familiar to him as his own,” whether Hannibal understood beforehand the degree to which the Romans would pack the middle remains open to question. Yet his experience fighting them would have warned him of their will and of their ability to break through in the center, and the likelihood of their trying it again. Also, given his knowledge of Greek military practice, he was doubtless familiar with the Athenian tactics at Marathon in 490, when the Greeks withheld their center and crushed the Persians with their wings.32 As the day of battle approached, all of this must have been taking root in Hannibal’s fertile brain as he roughed out the framework of an even more lethal trap. As we shall see, the final details would await the contingencies of the battlefield, but the basic plan of using the Romans’ own greatest strength against them was inherent in Hannibal’s deployments and therefore had to have been plotted in advance.

  Though there is a tradition of viewing Hannibal as simply being up to his usual tricks—hidden attackers and fake surrenders33—the key deception at Cannae was far more subtle. In essence, the trap was hidden in plain sight, something that even today does not seem to be fully understood. Basically he planned to string a line of combined Gauls and Spaniards between two very deep columns of Libyans positioned on either flank, so that viewed from above the formation would look like a backward block letter C. The idea was that as the legionaries rushed forward, the Gauls and Spaniards would give way in a measured fashion (this was critical), leading the Romans farther and farther in between the two columns of Libyans, who would then be in a position to stage a devastating simultaneous attack inward from either flank, stopping the Romans dead in their tracks and leaving them all but surrounded.

  Maps of the battle, which are invariably drawn from a bird’s-eye perspective, make the net results clear enough, but also reveal the central deception in a way that leaves open the question: “Why would anyone be dumb enough to walk into such an obvious trap?” But from ground level it would have been far from obvious.

  The analogy of American football is helpful. This very intricate game can be enjoyed and understood by the public precisely because it is viewed from on high; the deception is designed to be seen at ground level, and from this perspective deceptions are profoundly confusing, requiring all manner of coaching, cues, and experience so that players are not fooled on every play. As the Romans approached the Carthaginian line, all they would have seen was a continuous line of men, with no way of knowing the varying depth at either side. As the Romans pushed forward, their attention would have been focused straight ahead and toward the center, where they were making the greatest progress. When the Punic flanks attacked, most of the Romans would not have realized it was even happening. They would have known only that their body of men had strangely come to a halt. By this time it would have been too late. They were as good as dead.

  Assuming that Hannibal did not have direct knowledge of the Romans’ plans and simply had to anticipate what they might do, the Carthaginian’s plan faced several worrisome contingencies. Expecting his adversaries to pack the middle implied they would deploy on a fairly narrow front, not much wider than his own. Should the Romans march onto the battlefield in a more normal formation, their advantage in numbers would leave the Carthaginian line seriously outflanked on both sides, affording a perspective that would not only betray the depth of the Libyan columns, but also would force the Carthaginians to abandon the ambuscade by pivoting outward to make up the difference. Also, the Roman and allied cavalry could not be ceded the initiative; if they were allowed to sweep around to either side of the Carthaginians, the jaws of the trap would be revealed and their commanders could be warned before it was too late. None of this happened; instead the Romans played into Hannibal’s hands as if choreographed; but such schemes are always vulnerable to the unexpected and this could account for the shadow of what is possible to interpret as Plan B in the sources—Appian’s (Han. 20) story of Hannibal concealing some cavalry and light troops in ravines on a hill (presumably the bluffs leading up to Cannae34) with orders to attack the enemy rear as at Trebia, and Livy’s (22.48) tale of 500 Numidians staging a fake capitulation, being conducted behind enemy lines, and later producing hidden swords and assaulting from this quarter. Neither is taken very seriously by modern historians; but they were hardly out of character for a fox full of tricks.

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  As the sun rose on Tuesday, the second day in August, the scarlet tunic signifying battle could be seen displayed above the tent of Terentius Varro, whose turn it was to command the Cannae army. Polybius says Varro’s men were eager for the fight, were at a near fever pitch of anticipation from the waiting.35 Orders would have been distributed to the tribunes in the night. The tribunes then would have assembled the men and cavalry in time to march out of camp just after dawn, cross the river, and join the troops in the smaller encampment on the right bank. All were now present, with the exception of ten thousand (probably a legion and an ala) left to guard the main camp and stage an assault on the Punic encampment during the b
attle. It is likely that the men guarding the main camp were the bulk of those fated to survive the day and become the living ghosts of Cannae.36 Those less fortunate, around seventy-six thousand men, would move into the customary formation—velites out front; triplex acies, compacted in the middle; and cavalry on the flanks—all awaiting the Carthaginians and destiny.

  But exactly where were they? The short answer is that we will never know the precise site of the battle for sure; but that said, the issue has stirred up enough controversy over the years to make it worth considering. Geographically, there are basically two reference points—the location of Cannae itself and the River Aufidus, now called Ofanto. There are also two reliable historical artifacts: we know from Polybius that the battle was fought on the same side of the river as the smaller Roman camp, and the Roman line faced roughly south, with its right flank anchored by the river.37 It also makes sense that the Romans would have wanted their left flank resting against the highlands on which Cannae was perched, the idea being to make it impossible for Hannibal’s cavalry to sweep around either side to envelop them. The problem is that the distance between the bluffs and the modern Ofanto is far too narrow to accommodate anything like the size of the Roman army, no matter how compacted.

  This led a number of respected scholars to propose that the battle was actually fought on the left side of the river,38 or on a broad plain to the east of Cannae.39 But the problem with the first view is that it clearly contradicts Polybius, who seldom made this sort of mistake; the drawback to the second is that the flat area to the east is easily wide enough to give Hannibal’s cavalry complete freedom, which raises the question of why Varro would have bothered crossing the river to fight there. Yet all of these interpretations assume that the course of today’s Ofanto is identical to that of the Aufidus, likely a bad bet, given the passage of twenty-two hundred years. This assumption is questioned by modern historians Peter Connolly and Adrian Goldsworthy.40 Their ingenious alternative is that the ancient river ran considerably to the north as it passed Cannae, leaving flats of about 1.3 miles, wide enough to fit the Roman order of battle as it was assembled that day. This hypothesis remains open to conjecture, but this alternative location seems to be the most plausible for what would shortly become the most prolific killing ground in the history of Western warfare.

  If this was indeed the point of deployment for the Romans, it must have inspired great confidence. The inexperienced citizen and allied cavalry, stationed at the extreme ends of the line, right and left respectively, had been relieved of any offensive responsibilities; the cavalry had simply to guard the flanks while the infantry did its work.

  Similarly, the numerous but qualitatively inferior velites that were spread out in front of the army had no particular mission once the force was deployed, and they could conveniently retreat between the maniples if pressed.

  Meanwhile, the reinforced triplex acies seemed unstoppable, and if anything slowed it down, it was at least impenetrable. It must have appeared to Varro and Paullus that they had finally positioned their forces in a way that even Hannibal could not bend to his own advantage.

  Now it was his turn to do just that. Hannibal apparently sent the Balearic slingers and Numidian foot soldiers across the river at about the same time the Romans crossed, but the mission does not seem to have been to interfere with enemy deployments so much as to set up a perimeter behind which the Punic cavalry and heavy infantry could line up.41 When this was done and he was certain the Romans were ready to fight, Hannibal followed. We can conjecture that the cavalry crossed the river first to reinforce the screeners. Next the Gallic and Spanish infantry joined them, lining up in the center, followed by the two bodies of Libyans, who took their place on either side but remained in columns to form the backward block letter C. By this time the horsemen would have split apart and moved to the flanks, the Spanish and Gallic heavy cavalry on the left facing their Roman equivalents, and the Numidians on the right matched against the allied mounted elements.

  As orderly and purposeful as these pre-battle rituals seem in print, the real thing must have provided, even before the fighting started, plenty of distractions and cause for disorientation. At this point the field must have been a jumble of cacophony—horns blaring, drums pounding, swords beating on shields, shouts and war cries reverberating back and forth, to and fro—all the sounds that men muster as they steel themselves to face death and intimidate those they hope will be their victims. Also, more than 125,000 men and in excess of 15,000 horses tramping about in a confined area must have kicked up huge quantities of dust, and it appears that Hannibal’s familiarity with the environment now dovetailed with his desire that the Romans not accurately perceive the true nature of his infantry formation. He had apparently observed earlier that a southeasterly wind, the Vulturnus, gusted with increasing force during the morning, and could be counted on to whip up the dust and blow it into the Romans’ faces, a vexation apparently confirmed by a fragment from the near-contemporary poet Ennius.42

  Finally, and probably most important, this was August in southern Italy; we can count on it having been hot, and it was bound to get hotter as the day progressed. Most of the Roman heavy infantry and at least the rearmed Libyans would be burdened with between fifty and eighty pounds of arms and armor (see Chapter II, section 5) as they fought for their lives throughout the day. If Trebia had been orchestrated by hypothermia, Cannae was destined to be an inferno where untold thousands were likely to be felled by heat exhaustion, and access to drinking water may well have allowed the Carthaginians to persist in their butchery during the last and most murderous phases of battle.

  So it was as they began to fight. The ancient sources agree that the light troops were first to engage, and from Polybius we hear they were evenly matched, neither side gaining an advantage before withdrawing, as was customary, behind their respective lines of heavy infantry.43 If it had been otherwise, presumably we would have heard more from other sources. So it seems the velites’ numerical preponderance had won the Romans at least a standoff—an auspicious start, considering the multiple drubbings they had taken on earlier occasions. Still, the Punic auxiliaries may have inflicted a very significant casualty at the outset. Livy (22.49.1) reports that the consul Aemilius Paullus, who was with the Roman citizen cavalry, was dealt a severe head wound from a slinger just as the battle commenced—an injury bad enough to leave him unable to ride a horse and bad enough to force his bodyguard to dismount in order to protect him. Polybius does not mention this incident, but it is still suggestive, considering what was about to happen.

  The first decisive Punic move came when the Spanish and Gallic cavalry under Hasdrubal—leader of the service corps and destined to perform brilliantly on this day—charged headlong into the opposing horse on the Romans’ right flank. With their adversaries anchored on the river and outnumbering the Romans by more than two to one (around sixty-five hundred to twenty-four hundred), there were none of the normal wheeling maneuvers. Instead the Carthaginians seemed intent on going right through the Romans.

  The combat that ensued, Polybius (3.115.3) tells us, “was truly barbaric.” In large part this was because it was mostly on foot. Roman cavalrymen had a decided proclivity toward fighting on the ground, and many of these troopers must have been inexperienced and new to their mounts.44 But they also may have chosen to dismount because of Paullus’s wound. Plutarch maintains that when the consul was forced from his horse and his attendants got off theirs to protect him, the cavalry assumed a general order had been given and so also dismounted—a development that supposedly caused Hannibal to comment: “This is more to my wish than if they had been handed over to me in fetters.”45 While it is unlikely the Punic commander actually observed the cavalry getting off their horses, the act nonetheless proved fatal to most of the outnumbered Romans, who were basically annihilated. This is also where many of the Roman senators and others of the equestrian class would have gathered to fight, and ended up making their last stand. It is no
t clear if Paullus died here—he and his staff may have escaped to join the rest of the army—but Livy’s version makes it seem that this was his end. So at a point when the battle had barely begun, it seems logical that the republic had already been dealt a grievous blow. And it would only get worse. Rather than chase down the last of the survivors who managed to get back on their horses and flee, Hasdrubal reeled in his men from the pursuit, then rested and re-formed them to inflict further mayhem on another part of the battlefield.

  Meanwhile, the heavy infantry engagement had begun and had already taken shape, literally, in an unexpected way. As the line of Gallic and Spanish infantry advanced (one source estimates the formation was roughly 840 men wide and 26 deep46), it bowed outward to form a crescent. While some maintain this was natural for a line of men moving forward,47 others believe it was a last-minute decision on Hannibal’s part.48 Whichever it was, this convex formation had an immediate and beneficial effect for the Carthaginian side. For as the Roman hastati charged and reached pila-throwing distance, the shape of the line left only a narrow group in the Punic center vulnerable to this potentially devastating missile barrage, and may have led many legionaries to waste their shots while still out of range.49