Hannibal and the Second Punic War: What Polybius and Livy Tell Us

Hannibal's war on Rome from the Alps to Cannae and Zama, following Polybius and Livy and showing where their accounts and modern views differ.

Avevide · Last reviewed October 24, 2026 · 8 min read

In 218 BCE, the Carthaginian general Hannibal marched an army, with war elephants, from Spain over the Alps and into Italy. For more than a decade afterward, he fought on Roman soil. He destroyed Roman armies at the Trebia, at Lake Trasimene and, most famously, at Cannae. And yet Carthage lost the war, and Hannibal ended it defeated in Africa.

The Second Punic War is one of the best documented conflicts of the ancient world, largely thanks to two historians. Polybius, a Greek historian, questioned men who had been present, made the Alpine crossing himself and found a record left by Hannibal. Livy, a Roman historian, told the story at great length and with great drama. Where they agree, we stand on firm ground. Where they disagree, the arguments are still worth having.

This guide follows the war from its causes to its peace terms, and shows what the two main sources say, in public-domain translations, along with the questions modern historians still debate.

Why the war began

Rome and Carthage had already fought one long war, which ended in 241 BCE. Polybius, in W. R. Paton's translation, insists on separating the "beginnings" of the second war from its true causes. Carthage's siege of Saguntum in Spain and its crossing of the Ebro River were the beginnings, he says, but "I can by no means allow that they were its causes."

He names three causes instead. The first was "the indignation of Hamilcar surnamed Barcas, the actual father of Hannibal," who never accepted defeat in the first war. The second, which he calls "the second and principal cause," was Rome's seizure of Sardinia after that war, when Carthage was forced to give up the island and pay an extra 1,200 talents. The third was Carthage's success in Spain, which gave it the resources and confidence to fight again.

Polybius tells a famous story to show Hamilcar's influence. Years later, at the court of King Antiochus, Hannibal recalled that at nine years old he had stood at an altar while his father sacrificed before leaving for Spain. Hamilcar led him to the altar and had him swear "never to be the friend of the Romans."

Polybius also argues with an earlier Roman historian, Fabius Pictor, who blamed the war on the ambition of Hasdrubal, the Carthaginian commander who governed Spain before Hannibal, and claimed that Hannibal acted against the wishes of Carthage's leaders. Polybius thought this explanation did not hold up. Ancient historians, in other words, were already arguing about war guilt.

Hannibal took Saguntum "after eight months of hardship and anxiety," and Rome declared war.

Over the Alps

Polybius reports that Hannibal set out from Spain with about 90,000 infantry and 12,000 cavalry. The whole march from New Carthage took five months, and the crossing of the Alps itself took fifteen days. When he came down into the plain of the Po River, his surviving force numbered "twelve thousand African and eight thousand Iberian foot, and not more than six thousand horse."

That precise figure comes from an unusual source. Polybius says Hannibal recorded his numbers "in the inscription on the column at Lacinium," and explains elsewhere, about his figures for Hannibal's forces in Spain, that he found on the Lacinian promontory "a bronze tablet on which Hannibal himself had made out these lists during the time he was in Italy," which he chose to follow. He also claims firsthand knowledge of the route: he had "personally inspected the country and made the passage of the Alps to learn for myself and see."

Livy shows how uncertain the numbers were for other writers. In the translation by D. Spillan and Cyrus Edmonds, he notes that estimates ranged from "a hundred thousand foot and twenty thousand horse" down to "twenty thousand foot and six thousand horse." He was most tempted to trust Lucius Cincius Alimentus, who said he had been taken prisoner by Hannibal and who reported hearing from Hannibal himself that the army lost 36,000 men after crossing the Rhone.

Then there is the route. Livy was surprised "that it should be doubtful by what road he crossed the Alps," and he rejected two popular answers. Reviewing a short biography by Robert Garland, the historian Fred Drogula raises another puzzle: why did Hannibal face "such deadly opposition crossing the Alps in 218 BC when his brother Hasdrubal crossed apparently without opposition in 207 BC?"

The cost was real either way. After the battle at the Trebia, Polybius says, rain and snow killed "all the elephants" except one.

Trebia, Trasimene and the delaying dictator

Hannibal's first great victory came at the Trebia River in northern Italy. Within the first year of the invasion he also trapped a consular army at Lake Trasimene in Etruria. Polybius writes that about 15,000 Romans fell in the valley, including the consul Flaminius, killed by Celtic warriors.

Rome responded by appointing a dictator, Quintus Fabius, granted, as Polybius explains, the authority of "a general with absolute powers." Fabius refused to offer Hannibal a set battle. Instead, Polybius says, he followed the Carthaginians along the hills, keeping close without risking a decisive clash. His own master of the horse, Marcus Minucius, ran him down publicly for his "craven and slow conduct of the campaign." Later Romans remembered Fabius by the nickname Cunctator, the man who delayed.

Cannae, 216 BCE

The delaying strategy was unpopular, and in 216 BCE Rome met Hannibal at Cannae with a very large army. Hannibal's cavalry pressed on both flanks, and in Polybius's account the Romans were "gradually huddled in and surrounded" until almost all were killed.

The two sources disagree sharply about the scale. Polybius says that of the Roman infantry about 10,000 were captured, perhaps 3,000 escaped, and "All the rest, numbering about seventy thousand, died bravely." He puts Hannibal's losses at about 4,000 Celts, 1,500 Spaniards and Africans and 200 cavalry. Livy, in the Spillan and Edmonds translation, reports that "Forty thousand foot, two thousand seven hundred horse" are said to have been slain. Either way, the losses were staggering. Polybius drew a tactical lesson: it is "better to give battle with half as many infantry as the enemy and an overwhelming force of cavalry than to be in all respects his equal."

Livy adds a famous scene. Hannibal's cavalry commander Maharbal urged an immediate march on Rome, promising that in five days Hannibal would feast on the Capitol. When Hannibal hesitated, Maharbal replied: "You know how to conquer, Hannibal; but you do not know how to make use of your victory." Livy adds that "That day's delay is firmly believed to have been the preservation of the city and the empire."

Was Maharbal right? Historians disagree. Drogula notes that Garland, for one, suggests Hannibal's goals "may not have included the total conquest of Rome," so a march on the city may never have been the plan.

Why victory in battle was not enough

Hannibal's strategy depended on breaking Rome's network of Italian allies. Some did go over to him. After Cannae he wintered at Capua, one of the richest cities of Italy, during 216 to 215 BCE. But many allies stayed loyal.

Why did some communities defect and others not? In a review of Michael Fronda's book on southern Italy during the war, Mark Thatcher explains that earlier scholars looked for "a single key factor," such as the presence of Hannibal's army or hatred of Rome. Fronda rejects such explanations because "not all the allies (not even all the allies in a particular region) rebelled," and he stresses local circumstances and rivalries among each town's aristocrats.

Hannibal's own choices may also have hurt him. Drogula, discussing Garland's account, points out that Hannibal released his non-Roman prisoners in 218 BCE to win Italian support, but the next year ordered the killing of Italians, which Drogula calls "a counter-productive move."

Scipio, Zama and the peace

The war turned on other fronts. The Roman commander Scipio drove the Carthaginians out of Spain and, Plutarch says, returned to Rome to be made consul, for 205 BCE. Against the advice of Fabius, he took the war to Africa in 204 BCE. Hannibal left Italy in 203 BCE and returned to Africa.

The decisive battle came near Zama, a town Polybius places five days' journey west of Carthage. Hannibal put more than 80 elephants in front, with about 12,000 mercenaries behind them. Scipio lined up his units one directly behind another, leaving open lanes, and ordered his light troops to fall back through those lanes if the elephants charged. Scipio won, and the war ended in 202 BCE.

Polybius records the peace terms Scipio dictated. Carthage kept its own laws and territory in Africa but had to hand over prisoners and deserters, surrender its warships except ten triremes, along with all its elephants, and agree "not to make war at all on any nation outside Africa and on no nation in Africa without consulting Rome." It also had to pay "ten thousand talents in fifty years" and give a hundred hostages.

Reading Polybius and Livy

If you want to explore the war yourself, it helps to know how the two writers work.

Polybius is analytical. He separates causes from pretexts, argues with earlier historians and cites documents and eyewitnesses. His numbers are usually the more precise, though not beyond question.
Livy is dramatic. He gives speeches and memorable lines, like Maharbal's, and he is candid when his sources disagree, as with Hannibal's numbers and route.
Both wrote from the Greek and Roman side. Hannibal's own voice reaches us mainly through his bronze tablet and through the stories these writers chose to tell.

Readers today still face the questions these authors raised: who was really to blame for the war, which pass Hannibal used, how many men died at Cannae, whether he should have marched on Rome, and why Rome's alliance system held.

Key takeaways

The Second Punic War began in 218 BCE when Hannibal marched from Spain across the Alps into Italy, and it ended with his defeat near Zama and Rome's victory in 202 BCE.
Polybius blamed the war on deep causes, Hamilcar's indignation, the loss of Sardinia and Carthage's success in Spain, rather than on the siege of Saguntum.
Hannibal won crushing victories at the Trebia, Trasimene and Cannae, but the loyalty of many of Rome's allies denied him a strategic win.
Polybius and Livy disagree on key numbers, including Hannibal's army size and the Roman dead at Cannae, and even ancient writers could not agree on his Alpine route.
The peace terms ended Carthage's power to wage war without Rome's consent.

Sources

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