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Hannibal’s Big Mistake

By Richard Gabriel
10/26/2017 • Military History Magazine

In the Second Punic War the great Carthaginian general repeatedly defeated Rome’s best armies—but still lost.

In November 218 BC, after invading Italy, Carthaginian military commander Hannibal defeated a Roman cavalry force at the Ticinus River. A month later he destroyed a Roman consular army at the Trebbia River before retiring to Bononia (modern-day Bologna) to winter among the Gauls. In March 217 BC newly elected Roman consuls Gnaeus Servilius and Gaius Flaminius took command of armies intended to repel Hannibal— Servilius at Ariminum (modern-day Rimini) and Flaminius at Arretium (modern-day Arezzo). Servilius’ force blocked Hannibal’s easiest route along the Adriatic coast, while Flaminius covered one of the major outlets through the Apennines from Bononia, Hannibal’s most direct route to Rome. The consuls waited for Hannibal to move.

Meantime, the Gallic chiefs believed Hannibal was using them as cannon fodder and were restless that this war in their territory was bringing them little plunder or profit. They were anxious to raid Rome’s allies, first in Umbria and Etruria and then in Rome’s rural environs, the Ager Romanus, for plunder and revenge. As spring approached, Hannibal had to move the war away from Cisalpine Gaul or face abandonment by his Gallic allies.

And move he did. Indeed, Hannibal’s war against the Romans would prove a grave— if ultimately hollow—threat to Rome and all it represented.

Hannibal left Bononia in early spring “when the weather began to change,” according to Polybius. The easiest passage over the Apennines from Bononia was via the 3,100-foot Colline Pass. This route emerged not far from Arretium, where Flaminius and his army were deployed. Aware of the consul’s presence, Hannibal moved instead through Porretta Pass to Pistorium (modern-day Pistoia), 52 miles northwest of Arretium. This route allowed Hannibal to assemble his army without opposition on the Etruscan plain.

Once out of the mountains, Hannibal found his way blocked by the wide and flooded Arno River marshes. His troops had to wade through deep water, at times sinking over their heads in swirling eddies. Many drowned, while others gave up and died where they fell. Men heaped the corpses of dead animals in piles to rest upon and many promptly fell ill; Hannibal himself caught an infection that ultimately cost him the sight in one eye. The four-day crossing allowed the troops little rest, and losses among the men must have been considerable— Polybius reports the Gauls suffered the most casualties.

Losses were also high among the horses and pack animals, according to both Polybius and Livy. If the ancient historians are correct, then Hannibal may have had to confiscate every mule and donkey on the Etruscan plain to reconstruct his pack train. Cavalry horses were a more serious matter. Horses were expensive and uncommon among farmers. Even if Hannibal had been able to acquire sufficient horses, they would have taken weeks to train for war. It is likely, then, that Hannibal’s cavalry contingent was substantially reduced.

The Etruscan plain was among the most agriculturally productive regions in Italy, and as soon as Hannibal cleared the marshes, he encamped and sent out foragers for food and animals. He also dispatched reconnaissance units to determine the movements of the Romans at Arretium and “the lie of the country to his front.” Although ancient historians give the impression that Hannibal almost immediately began his movement south, he likely required several weeks to replenish his army. Flaminius failed to detect Hannibal’s position in time and missed an opportunity to attack him as he emerged from the swamps with his weakened army. Only after Hannibal had already begun to move south, passing close to Arretium, did Flaminius become aware of Hannibal’s position, too late to place his army between Hannibal and Rome. The Roman consul had no choice but to follow in Hannibal’s wake, hoping to bring him to battle.

Hannibal’s route toward Rome took him through the village of Borghetto along a road skirting the north- ern shore of Lake Trasimene toward Passignano. Beyond Borghetto the terrain narrowed, with the lakeshore on one side and cliffs on the other. Beyond the narrow passage the terrain opened into a flat rectangular valley floor with steep hills on one side and the lake on the other. At the far end of the valley the road ran up a steep hill. As Hannibal marched his army over this route, he noticed a thick morning fog rising from the lake that made visibility difficult. He moved his Spanish and African infantry to the hilltop at valley’s end and pitched camp. He then arranged the rest of his army along the hills running up from the lakeshore, hiding his Gallic infantry in the hills and placing his cavalry in concealment just inside the valley entrance.

Flaminius moved his army through Borghetto toward Passignano and made camp for the night but failed to send reconnaissance parties into the valley. He assumed Hannibal was moving away from him, and his plan was to catch the Carthaginian’s army on the march, engage and defeat the rear guard, and then attack the main body before it could turn and face the Roman assault. When Flaminius marched his army through the narrow defile onto the widening plain at dawn the next day, he could see Hannibal’s encampment atop the hill at the valley’s exit. The Roman consul thought it was Hannibal’s rear guard and ordered his forward elements to engage. With the rest of the Roman column still in line of march, its advance units rushed uphill, thinking they had taken Hannibal by surprise.

Near the top of the hill the Romans ran headlong into Hannibal’s infantry, and a fierce battle ensued. On the valley floor Flaminius’ army got through the narrow defile, its head moving up the hill at the far end of the valley, its tail extending almost back to the valley entrance. With the Roman advance blocked by his infantry, Hannibal gave the trumpet signal for the hidden Gallic infantry to attack the Roman column’s flanks. At the same time his cavalry—concealed inside the entrance passage—struck the Roman rear. In the three-hour battle, Hannibal destroyed the Roman army—Livy and Polybius record a toll of 15,000 Roman soldiers killed at a cost of only 1,500 to 2,000 of Hannibal’s men. The Carthaginians captured more than 6,000 Romans and allied soldiers. Flaminius himself was killed.

While Flaminius was trailing Hannibal toward Lake Trasimene, Servilius received orders to redeploy and link up with his fellow consul. The shortest route to Rome and Lake Trasimene was down the 140-mile Via Flaminia, which linked the capital to Ariminum. Servilius sent 4,000 cavalry under the command of C. Centenius on ahead of his main force. But Hannibal’s reconnaissance picked up Servilius’ movement, and Hannibal sent his cavalry commander, Maharbal, with a strong force to intercept Centenius. Maharbal ambushed and annihilated the Roman cavalry somewhere near Assisi, about 20 miles from Lake Trasimene. The ambush put an end to Servilius’ movement, and he returned to Ariminum where he soon came under attack by the Gauls.

Was Flaminius aware of Servilius’ attempt to come to his aid? If so, he may have thought he was driving Hannibal into a trap. With his own army behind Hannibal, and Servilius moving down the Via Flaminia, Flaminius may have thought the two Roman armies could catch Hannibal between them somewhere in the Tiber River Valley beyond Perugia. It was a strategically sound plan and may well have quickly ended the Second Punic War had it worked. By luck or genius Hannibal led Flaminius into an ambush at just the right time, before Servilius could arrive on the battlefield. With Flaminius out of the way, Hannibal turned to blunt Servilius’ advance with his cavalry and did so with great success. The result of both engagements was that the Roman army had been neutralized. The road to Rome was now open.

But was Hannibal’s army sufficiently powerful to attack and conquer Rome?

When Hannibal fought at the Trebbia he had just over 40,000 men, some 14,000 of whom were Gauls recruited in the Po Valley. Hannibal spent the winter relatively comfortably in Bononia, though the Gauls remained anxious to attack Etruria. Over that winter Hannibal attracted perhaps 10,000 to 15,000 additional men and cavalry to his cause, thus the army that marched south in the spring is thought to have numbered between 50,000 and 60,000 men. Even with the losses Hannibal suffered during the passage of the Arno marshes, he still would have had an army of 50,000 to 55,000 after Trasimene with which to attack Rome.

Hannibal replenished his pack train with confiscated mules and donkeys from the countryside, and he captured 4,000 additional pack animals and 2,000 cavalry horses from the Romans at Trasimene. Maharbal captured another 4,000 Roman cavalry horses in his engagement against Servilius. These captured Roman cavalry mounts replaced the horses Hannibal lost crossing the marshes, returning his cavalry to full strength. Moreover, Polybius notes that Hannibal was able to reequip his light infantry with weapons and armor taken from the Roman dead at Trasimene. The Carthaginians also captured large quantities of other supplies, including food, clothing, tents, tools, boots, blankets, canteens, saddles, bridles and grain for the horses.

Rome lay just 80 miles south of Hannibal’s camp, less than 10 days’ march, and no sizeable Roman military force stood between Hannibal and the capital. The previous year’s Roman military buildup put 11 regular legions in the field: two with Flaminius at Arretium, two with Servilius at Ariminum, and one in Tarentum; the others were stationed abroad. Hannibal had already destroyed Flaminius’ legions, and Servilius, having lost his cavalry, had retreated to Ariminum and was engaged in a running battle with the Gauls. So only two irregular legions, the legiones urbanae, remained in Rome to defend the city. But Rome had only recently authorized these legions, and it is unclear whether they were at full strength and equipped or even trained for battle.

Hannibal held yet another advantage. In June a fleet of 70 Carthaginian warships—some 60 percent of Carthage’s total naval strength—had arrived off Pisa on the Etruscan coast, only 80 miles from Hannibal’s camp. One plausible reason for the fleet’s appearance is that Hannibal’s original operational plan was to invade the Italian peninsula in a combined operation with the Carthaginian navy. Such an audacious operation likely presaged an attack on Rome itself. The navy was to prevent the Roman troops in Sicily or Sardinia from coming to the aid of the city. The last known disposition of the 220-ship Roman fleet was in the summer of 218 BC. At that time Sempronius had taken 10 ships with him to Ariminum on the Adriatic, leaving behind some 150 to protect Sicily. Another 30 ships were on duty with the Scipios in Spain. Thus, only 30 or so ships were available to protect the capital. The arrival of 70 Punic warships off the Etruscan coast gave the Carthaginians a numerical advantage in the immediate theater of operations.

With all these forces at his disposal, why didn’t Hannibal attack Rome? Historians have suggested two reasons: First, that Hannibal’s army was not large enough to invest Rome, given the size of the city and its garrison. Second, that an effective blockade of Rome was impossible so long as the Roman navy kept open a lifeline to the sea along the Tiber River, on which supplies could reach the city’s garrison. Neither reason seems sufficient to explain Hannibal’s actions.

The population of Rome in republican times numbered between 450,000 and 500,000 citizens, all living within an 8.4-square-mile area enclosed by the Servian Wall, a 33-foot-high stone barrier some 7 miles in circumference. Five gates breached the wall, each at the terminus of a major road leading to the city. On the side of the wall facing the open country was a 30-foot-deep defensive trench. There was nothing particularly formidable about such defenses, given Carthaginian engineering ability. Hannibal could quickly construct sufficient siege equipment to carry out an attack. Most of the city’s military-age men—some 50,000—were already serving with the legions in the field. Even if the two recently raised irregular legions were fully trained and equipped, 10,000 soldiers were simply insufficient to defend the miles of wall and multiple gates against an attacking army of 50,000. Plutarch, in his Life of Marcellus, concedes the Romans did not have enough men to defend the walls.

The second argument, that a successful attack on Rome would require Hannibal’s navy to blockade the Tiber and thus prevent resupply, assumes that Ostia was Rome’s main port at the time, when in fact it would not become a major port until the reign of Emperor Claudius (AD 41–54). In Hannibal’s time Rome’s main supply lifeline was not the Tiber but the port of Puteoli (modern-day Pozzuoli), 120 miles south of the capital. The Romans transported supplies landed at Puteoli overland by road. Thus Hannibal could have cut off Rome’s supplies simply by blocking the roads from Puteoli, leaving his navy free to attack the Roman troop transports carrying relief forces.

By his own admission, Hannibal’s failure to attack Rome was his greatest mistake. Had he assaulted the capital after Trasimene, either as a genuine effort or as a feint, Rome would have been forced to recall some of its legions from abroad, exposing Sicily, Spain or Sardinia to a Carthaginian invasion. The nearest available legions were on Sardinia—but those 70 Carthaginian warships lay between them and the mainland. Nothing would have demonstrated Rome’s weakness to its allies more than Hannibal’s capture of the very capital. Even an unsuccessful attempt might have shaken Rome’s political will to fight, made it more difficult to raise new legions and, perhaps, changed the course of the war.

Hannibal had shown great prowess against the Romans in the field: In less than a year (November 218 BC–June 217 BC) Hannibal had dealt the Roman legions one defeat after another. Ticinus had cost the Romans upward of 2,000 men. The engagement at the Trebbia had claimed more than 25,000 Roman and allied soldiers. And at Trasimene, Hannibal had killed 15,000 more Roman troops, captured 6,000 and eliminated a major Roman commander; the Carthaginians had then ambushed a late-arriving Roman relief force, at a cost of 4,000 more men. All told, Hannibal had killed or captured some 50,000 Roman soldiers, a number equal to 10 legions, nearly half of that number in a single week. And yet he did not attack Rome when he was at his strongest and Rome perhaps weaker than it would ever be again. So why did Hannibal, one of history’s great military gamblers, refuse to roll the dice?

Simply put, Hannibal did not attack Rome because he did not think it necessary. In his view he had already conquered Rome by crushing its legions. Like most Carthaginian aristocrats of his day, Hannibal was a Hellene in his thinking, training and understanding of history. He saw grand strategy as relatively straightforward. If one state invaded the territory of another, won a few battles and caused sufficient disruption, it was reasonable to expect one’s enemy would seek terms. The expectation that wars were ultimately settled by negotiation had become the norm in Hellenistic warfare, and it is reasonable to surmise that Hannibal accepted it as well. His strategic plan was predicated upon the assumption that Rome would behave in the conventional Hellenistic manner once the contest of arms had been decided.

Hannibal failed to understand the conservative culture and moralistic values that shaped the Roman view of war. The Romans considered Hellenes soft and corrupt, and their response to Hannibal’s victories was to raise more legions and keep on fighting. It was this prodigious effort that permitted the republic to raise and maintain its armies in the field, whatever the cost. It is estimated that nearly all fit male Roman citizens served in the army at some time or other during the war with Hannibal. For some periods as many as half of all eligible men were under arms. Of a military manpower pool of 240,000 male citizens, fully 120,000 died in the war, and it is possible that some 80,000 of them died as the result of combat, the rest from disease, shipwreck or accidents. Hannibal was facing an enemy that simply did not give up and would not negotiate on his kind of terms.

He should have learned that lesson from the aftermath of the Battle of Cannae in 216 BC. In the wake of that decisive victory he’d sent Carthalo, one of his cavalry commanders, with a delegation of Roman prisoners to negotiate a ransom with the Roman Senate. A Senate official met Carthalo outside the city walls and informed the Carthaginian he would not be received. The Romans would not parley. The Senate ordered Carthalo to depart Roman territory by nightfall. Furthermore, it not only rejected the prisoners’ plea that their ransom be paid but also sent them back to Hannibal. Romans always saw war as a relentless struggle and were willing to negotiate only as victors.

It remains one of Hannibal’s greatest failures that he never fully understood the enemy he was fighting. This failure left him to win battle after battle, only to lose the war.

 

For further reading Richard Gabriel recommends his own Hannibal: The Military Biography of Rome’s Greatest Enemy and J.F. Lazenby’s Hannibal’s War: A Military History of the Second Punic War.

Originally published in the November 2011 issue of Military History. To subscribe, click here

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