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  • James Houser

August 2, 216 BC - Battle of Cannae

Updated: Jun 12, 2021

August 2, 216 BC. The Roman Republic is ready to put an end to Hannibal and his invading army once and for all. They have assembled the largest army in their history, outnumber their foe two to one, and are ready to drive a stake into the heart of Carthage. Sadly, things aren’t going to go as planned. Welcome to history’s perfect battle: the Battle of Cannae.

On June 21, I described Hannibal’s invasion of Italy, especially his crossing of the Alps and his victory at Lake Trasimene. If you want, you can refresh your memory here: (POST LINK.) If you’re reading this on the toilet and want to finish it quickly, I’ll give you a review.

Hannibal is one of ancient history’s great figures, a legendary general famously consumed by his desire for vengeance against Rome. His city of Carthage had suffered terrible and humiliating defeats at Roman hands in the First Punic War from the 260s to 240s BC.

Hannibal and his brothers had accompanied their father to Spain, where their Barca family built up a new Carthaginian empire and organized a powerful army. On his father’s death, Hannibal took over, and by 218 BC decided that it was time for revenge. After starting a war with a local Roman ally in Spain, he led his army on its long march over the Alps and into Italy. It was payback time.

Two years later, Hannibal had won two enormous battles and brought the Roman Republic to a point of crisis. At the Trebbia River (218 BC) and Lake Trasimene (217 BC) Hannibal hadn’t just defeated Roman armies; he had come close to destroying them. Not only that, he was now loose in central Italy itself, poking around the outskirts of Rome. The Republic was in desperate straits with Hannibal at the gates, and the people were in near panic. They were in understandable fear for the very existence of their city

To everyone’s surprise and relief, Hannibal’s lethal veteran army had bypassed Rome and headed for southern Italy. It was never part of Hannibal’s strategy to attack Rome itself; such a siege was likely to fail. Instead, Hannibal wanted to tear apart the entire Roman alliance system in southern Italy. Multiple cities like Capua and Tarentum, and the mountain peoples like the Samnites, had only recently been brought under Roman rule by force. Hannibal hoped to find allies amongst these reluctant Roman possessions, and possibly to break them away from Rome altogether – permanently reducing the power of Carthage’s nemesis.

After the defeat at Lake Trasimene, the Senate took the extreme step of appointing a Dictator. This was often done in times of emergency or peril, but we shouldn’t read too much into the modern definition of the word. A dictator was invested with the full authority of the state, true, but his term only lasted six months and he could only act within his appointed sphere of authority. For the emergency of Hannibal’s invasion – the greatest emergency Rome had faced in a very long time, one that put the whole existence of the Republic at risk – the Senate appointed Quintus Fabius Maximus.

Most Roman generals of the period were of the “knock heads and ask questions later” type, men whose creed was “when in doubt, attack.” Fabius was rather more thoughtful and philosophical than the usual Roman, and much more strategic. He adopted a strategy for dealing with Hannibal that ran counter to every Roman instinct. The Romans would AVOID battle with Hannibal at all costs. Since Hannibal had won so many battles, and actively sought to engage the Romans in another major battle, Fabius was committed to denying him exactly this. This did not mean Fabius was passive; his army constantly shadowed Hannibal’s, and cut off and destroyed any small Carthaginian detachment, but resolutely refused to engage Hannibal’s main body in open combat. This led ever after to strategies of avoidance, delay and attrition being known as “Fabian strategy.”

Fabius’ strategy did not make him very popular. Hannibal marched up and down Italy, burning farms and towns wherever he went. Hannibal actively sought to draw the Romans into another confrontation; as things stood, Fabius’s game of “Not-touching-you” was wearing Hannibal down psychologically and materially. Hannibal took the unusual political step of burning every farm in one district EXCEPT for those owned by Fabius himself, as a way of undermining his opponent’s political legitimacy back in Rome.

Fabius had some close calls. In one case, a Roman general under his command named Minucius decided that he was a wimp and that they should fight Hannibal. At the Battle of Geronium, Hannibal tore into Minucius’ force before Fabius arrived to save him. On another occasion, Fabius had Hannibal trapped in a valley with all the mountain passes closed off. Hannibal strapped lit torches to the backs of a herd of oxen and had them driven towards one of the passes; when Fabius’ army ran off to intercept what they believed to be a breakout, Hannibal and his army slipped out behind them.

The Roman public grew increasingly frustrated with Fabius. To be fair, it can’t be hard watching your homes and farms – your homeland – being burned to the ground while your army just stands by and lets it happen. Fabius could argue that he wasn’t losing any more battles to Hannibal, true, and he had a solid argument that he was slowly wearing Hannibal down by attrition instead of direct action. From the Roman perspective, though, it didn’t look like winning. So when Fabius’ term as Dictator expired, the Republic elected two new Consuls: Gaius Terentius Varro, an advocate of a more aggressive war strategy, and the more flexible Lucius Aemilius Paullus. These two men would lead Roman armies throughout 216 BC.

Varro and Paullus decided to put together an army so huge that Hannibal would choke to death trying to swallow it. Normally the Senate only called forth 40,000 soldiers per year, but they decided to double it in 216 BC to deal Hannibal his lethal blow. The result was that the Romans would field almost 86,000 soldiers to troop off and confront their nemesis – the largest army ever assembled in Roman history. It would be like the United States committing the whole Army, the whole National Guard, and the Army Reserve into a single massive force designed to win the war in a stroke. Just so I can give you all some perspective for what happened next.

At this point, one of the quirks of the Roman political system became a problem. The two Consuls were equal in rank, and normally each would command his own army. Since they were going to be commanding a combined force sent to stop Hannibal, though, Roman law required them to rotate command on a daily basis. Hence the cautious and thoughtful Paullus would command one day, and the aggressive Varro the next. This isn’t even a way to run a glee club, let alone an army carrying your nation’s entire future in its hands, but that’s how the Romans operated, and that’s how the Roman army marched on its way to fight Hannibal at a small south Italian town called Cannae.

It’s worth talking about the two armies before we discuss the battle. The Roman army of the pre-Marius Republican era was an armored heavy infantry machine, as subtle as a kick to the groin and about as effective. It advanced in the three lines of hastati, principes and triarii based on the age and social class of it members. Its soldiers fought in heavy mail with short stabbing swords and tall shields, all provided at their own expense. Its men were citizens and only served when called, rather than being professional soldiers, so it was essentially a citizen army that went to fight Hannibal rather than the legion of film and fiction. The citizens of a Roman Republican army fought in tightly packed infantry formations that would bulldoze anything in their way.

In contrast, Hannibal’s army in Italy looked like a who’s who of the western Mediterranean. The core of his army were the solid Spanish and African foot soldiers that had served first his father, then him for years. Unlike the Romans, Hannibal had an impressive cavalry arm, with the Algerian light cavalry (the best in the ancient world) and heavier Spanish cavalry as his main striking arm. Finally, Hannibal had recruited heavily among Rome’s northern neighbors, the Gaul. These tribesmen were not as well-equipped or as disciplined as his own soldiers, but they were willing to fight against their great Roman enemy – especially alongside a general as charismatic and legendary as Hannibal.

Hannibal, knowing about the strange command structure of the Roman army, marched out to fight his foe on a day that he knew the aggressive Varro, rather than more thoughtful Paullus, was in command. Hannibal drew his forces up in an unusual formation. His line thrust forward into a shallow “V” shape, his most vulnerable and least trustworthy troops – the Gauls – at the apex of the V. To either side of them were his tougher and more reliable Spanish and African infantry, forming either point of the V, and to the outer edge of these men were his cavalry. One side – the left - had the heavy Spanish and fierce Gallic cavalry, while the other side had the nimble Algerian light cavalry.

Paullus saw this strange formation, and urged Varro to be cautious when the Romans marched out to fight Hannibal on August 2, 216 BC. The open fields of southern Italy baked under the summer sun as the Roman sledgehammer trudged forward in a big, sweaty, clanking column, its 86,000 men homing in on Hannibal’s 50,000. This was going to be the day that the Romans ended this stupid war once and for all. Hannibal, the burner of their farms and lands, the general who had somehow defeated a Roman army twice, could not hope to stand against the crush of almost 90,000 heavily armored soldiers slamming through the center of his line. Today would be the day it all ended.

The Roman infantry column crunched into the Gauls at the tip of Hannibal’s “V”, and began forcing them inevitably back like a buzzsaw. Hannibal himself was positioned with his Gallic allies, and rode behind them to steady them and give them encouragement – and, most importantly, to reassure them that they weren’t being sacrificed. As the Roman juggernaut ground the Gauls back, they followed Hannibal’s orders – and slowly fell back, just as planned.

See, Hannibal knew how the Romans fought, and knew what Varro’s tactics were intended to achieve. Varro wanted to split the Roman army in two by punching through the weak center. So Hannibal planned what history has remembered as the perfect battle: he was going to give Varro exactly what he wanted, and in so doing lead the Roman army to his doom.

As the Romans pushed forward against the Gauls, the African and Spanish infantry on either side maintained their position. The Roman advance inverted Hannibal’s “V”, pushing back the Gauls but leaving the veterans in place. The Roman commanders thought they were winning: they were moving forward and about to crack Hannibal’s line. Instead, they were marching into an enormous trap; the farther forward they went, the deeper into the trap. It only remained for the trap to be sprung.

While the infantry had been fighting, the Roman and Carthaginian cavalry had been skirmishing on the flanks. At Hannibal’s signal, though – when the Romans had advanced far enough – the heavy Spanish and fierce Gallic cavalry on the Carthaginian LEFT charged and scattered the Romans in front of them. Rather than chasing their fleeing opponents, the horsemen spurred their mounts around the rear of the advancing Roman infantry and smashed into the Roman cavalry on the Carthaginian RIGHT. The surprised cavalry fled here too. Now the combined forces of both Carthaginian cavalry units were unopposed. Now it was time to spring the trap.

As Hannibal gave his second signal, his Gauls, falling back this whole time, suddenly stood firm. At the same instant, the African and Spanish infantry swung 90 degrees onto either side of the Roman block of men. At the same instant, Hannibal’s combined cavalry units pivoted around and smashed into the Roman rear. The Romans were completely, utterly, surrounded, and the summer air of southern Italy resounded with the clash of metal and the screams of dying men as the great mass of Roman humanity was slowly, inexorably, slaughtered.

This process was not immediate; it took hours. Men in the center of the block were squeezed nearly to death as Hannibal’s army crushed them in its vise. As the day wore on, the Africans, Spaniards, and Gauls of the multiethnic army hacked their way through the largest Roman army ever fielded. It had done the Republic no good. Hannibal’s brilliant tactics had resulted in the greatest defeat in Roman history, and by nightfall at least 67,500 Romans were dead or taken prisoner on the field of Cannae. For all this, Hannibal only suffered around 6,000 casualties.

The Battle of Cannae was the Roman Republic’s darkest hour. Their army was virtually gone, annihilated in a single stroke, and Hannibal was virtually unopposed. The city flew into a panic, since everyone was convinced that Hannibal was about to march on Rome itself and take it, putting an end to their nation’s existence once and for all.

Hannibal did not march on Rome. The Romans themselves viewed this as his greatest mistake, but there are many conflicting arguments one way or another for whether it was a good idea or not. It certainly wasn’t part of Hannibal’s strategy, which was to strip Rome of its allies and subjects before forcing it to make peace. Hannibal, in fact, thought the Romans would HAVE to make peace after Cannae; any other country in the ancient world would have done the same.

The Romans, uniquely, did not; they vowed to fight to the end no matter what, even as the survivors of Cannae told terrible tales of Hannibal’s invincible army and as tens of thousands of their men lay dead on the field. Paullus himself had perished in the battle, along with 80 senators, 29 military tribunes, and many other Roman notables. In short, for any country but Rome, the terrible defeat at Cannae should have ended the war. But Rome would not surrender, even after the greatest military disaster in their history. And Hannibal had no answer to that.

Historians ever since 216 BC have regarded Cannae – where a smaller army surrounded and destroyed a larger one – as something like “the perfect battle,” the ultimate in military art that all generals aspire to. It’s one of history's most famous crushing victories, famous enough that “achieving a Cannae” is a military byword for achieving an overwhelming, shattering victory. Alfred von Schlieffen’s frankly unhealthy obsession with Cannae led him to develop the Schlieffen Plan, the idea for Germany to win the next European war in a single stroke by surrounding and destroying the French army. People like Frederick the Great, Robert E. Lee, George Patton and Norman Schwarzkopf have all cited Cannae as their ultimate aim in their risky, violent, confrontational tactics.

Everyone wants a Cannae…but a LOT of these people forget one key fact. Cannae didn’t end the war, it didn’t secure victory for Carthage. Because Rome won. Sometimes victory in battle is just not enough.

Tune in on September 16 to find out how Rome eventually turned the tables on their nemesis, their nightmare, their most terrible enemy – Hannibal of Carthage.

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