Why didn’t Hannibal attack Rome after Cannae?

“You know how to conquer, Hannibal”

The famous scene is in Livy. On the evening of Cannae, while Hannibal’s officers crowd round to congratulate him and urge him to rest his tired men, his cavalry commander, Maharbal, says there is no time to lose. In five days you will dine as a victor on the Capitol, he tells him. Follow me: I will ride ahead with the horsemen, so the Romans learn you have arrived before they learn you are coming. Hannibal praises his zeal but asks for time to think it over.

Of a truth the gods have not bestowed all things upon the same person. You know how to conquer, Hannibal; but you do not know how to make use of your victory.

Livy adds his own verdict: that one day’s delay, it was widely believed, saved the city and the empire. But Livy wrote under Augustus, almost two centuries later. Polybius, who wrote within living memory of the war and questioned men who had served in it, does not tell the story at all. The exchange may be a tradition that Livy polished.

What stood in the way

• Distance. Cannae lies about 300 kilometers (190 miles) from Rome as the crow flies, farther by road over the Apennines. And horsemen cannot climb walls.
• Walls. Rome sat inside the Servian Wall, built of volcanic stone in the fourth century BC after the Gauls had sacked the city: about 11 kilometers (7 miles) around and up to 10 meters high in places.
• Men. Soon after the news, the Senate named a dictator, Marcus Junius Pera, who enrolled four new legions, taking boys of seventeen and even younger, and armed 8,000 slaves bought by the state.
• Siege craft. Hannibal had no siege engines with him. Sieges were his weak point. Saguntum, in Spain, had held him up for eight months. After Cannae even little Casilinum, held by a small garrison from Praeneste and Perusia, held out against his army through the winter.

What Hannibal wanted

Hannibal had never planned to destroy Rome. He wanted its Italian allies to desert and the Senate to accept a peace that would cut Rome down to size. Livy has him tell the Roman prisoners after Cannae that he was not waging a war of extermination; he was fighting for honor and for empire. He let the captives send ten envoys to Rome to ask for their ransom, and a Carthaginian noble, Carthalo, rode with them to sound out peace. A lictor met Carthalo before he reached the city and ordered him off Roman soil by nightfall. For a while the plan seemed to work: Capua and much of the south came over to him.

Hannibal at the gates, five years late

He did come, once. In 211 BC, trying to pull the legions away from his besieged ally Capua, he marched north and camped by the river Anio, about three Roman miles (4.5 kilometers) from Rome. Then he rode up to the Colline Gate with 2,000 horsemen to look at the walls. Twice, Livy says, the two armies lined up for battle, and twice a violent storm of rain and hail drove them apart. The Romans showed their contempt by auctioning the very land his camp stood on, and it sold at full price. Hannibal answered by putting the bankers’ shops around the Forum up for sale, and marched away. Capua fell anyway.

Did he miss his chance?

Livy says that when Hannibal finally sailed home in 203 BC, he cursed himself for not leading his army straight to Rome while it was still bloody from Cannae. Most modern historians think he was right the first time. A worn army without siege engines could not have taken Rome in 216 BC. What beat him was not the walls alone but the city’s refusal to bend (why he lost the war).