What happened at the Battle of Cannae?

Rome goes for a knockout

After the disasters at the Trebia and Lake Trasimene, Rome had spent months on Fabius’s slow war, shadowing Hannibal and refusing battle. By 216 BC the voters had had enough. They elected two consuls, Lucius Aemilius Paullus and Gaius Terentius Varro, and gave them eight legions with as many allied troops, about 80,000 men. Rome had never put so many into one field. The plan was simple: crush Hannibal with numbers.

Hannibal chose the ground. He seized the Roman supply depot at Cannae, a hilltop in Apulia, today’s Puglia, above the river Aufidus, now the Ofanto, where open plain suited his horsemen. He had a little over 40,000 infantry and about 10,000 cavalry, Polybius says. The consuls took command on alternate days, and the day of battle was Varro’s. Plutarch tells of an officer, Gisco, unnerved by the size of the Roman army. Hannibal answered that in all that multitude there was not one man called Gisco, and his staff burst out laughing.

The trap

Varro packed his maniples closer together and made his lines many ranks deep, a battering ram meant to smash through the center. Hannibal put his Gauls and Spaniards in the middle and pushed them forward in a crescent, bulging toward the Romans. At either end of that crescent stood his best infantry, African veterans now armed with Roman weapons taken at earlier battles. His heavy cavalry, under Hasdrubal, held the wing by the river; the Numidian light horse held the other. Then the battle unfolded in four moves:

1. The cavalry. Hasdrubal’s horsemen broke the Roman cavalry by the river, then rode around behind the Roman army to help the Numidians scatter the allied horse on the far wing.
2. The center. The legions drove the crescent back until it bent the other way, and they poured into the hollow.
3. The wings. The African infantry, so far untouched, turned inward against both Roman flanks.
4. The rear. Hasdrubal’s cavalry came back and fell on the legions from behind.

The Roman army was now surrounded by one little more than half its size. Hannibal had made the double envelopment: the center gives way, the wings close in, the cavalry seals the back door.

A day of killing

By evening the Romans were packed so tightly they could barely swing their swords. Polybius gives 70,000 dead and about 10,000 captured. Livy gives 45,500 infantry and 2,700 cavalry killed. Hannibal lost about 5,700 men by Polybius’s count, most of them Gauls of the center, who had taken the shock. Paullus, wounded early by a sling stone, refused a tribune’s offer of a horse and died on the field. Livy lists among the dead two quaestors, twenty-nine military tribunes and eighty men of senatorial rank. Varro escaped to Venusia with about seventy horsemen.

The survivors were shipped to Sicily in disgrace and kept there for years. Some of them had their revenge in 202 BC, when Scipio took them to Africa and beat Hannibal at Zama.

Where it happened, and why it is still studied

Cannae stands on a low hill near Barletta. The ruins there, Canne della Battaglia, have a small museum, and scholars still argue about which bank of the Ofanto the armies fought on. The battle became a model studied ever since: a smaller army had surrounded and destroyed a larger one. In the early 1900s the German chief of staff Alfred von Schlieffen studied it so closely that he wrote a series of essays called Cannae. Rome’s answer to the disaster, and Hannibal’s choice not to march on the city, are their own story (why he did not attack Rome).