Hannibal: Fifteen Years Inside Enemy Territory

In 218 BCE a Carthaginian army left Spain, crossed the Pyrenees, crossed the Rhône, and then crossed the Alps in autumn with elephants. Roughly half of it died on the way. What arrived in northern Italy was perhaps twenty thousand infantry and six thousand cavalry, exhausted and far from any friendly port.

Over the next three years that force destroyed Roman armies at Trebia, Lake Trasimene and Cannae. Then it spent twelve more years in Italy achieving nothing decisive.

Why the Alps

The obvious route to Italy was by sea, and Carthage had been a naval power. But Rome had taken Sicily, Sardinia and Corsica in the previous war and controlled the western Mediterranean. Landing an army by sea meant losing it to the Roman fleet.

The overland route was chosen because it was the only route available. It also delivered Hannibal into Cisalpine Gaul, where tribes recently conquered by Rome were willing to supply him with men.

Cannae

At Cannae in 216 BCE Hannibal faced a Roman army roughly twice his size, which Rome had assembled specifically to overwhelm him by weight of numbers.

He arranged his centre in a forward curve of his least reliable troops, with his best infantry on the flanks and his stronger cavalry on the wings. As the Romans pushed into the centre, it gave way slowly, drawing the Roman mass forward into a shrinking pocket. The flanking infantry then turned inward while the cavalry, having driven off the Roman horse, came round and closed the rear.

The Roman army was surrounded in its own formation, too tightly packed to use its weapons. The casualty figures given by ancient sources run to tens of thousands in a single day.

Cannae is still taught. The double envelopment it demonstrates has been studied by staff colleges continuously since the nineteenth century.

Why It Was Not Enough

After Cannae, Hannibal did not march on Rome. Whether he could have taken it is debated. He had no siege train, Rome's walls were substantial, and his army had just fought a battle.

More to the point, his strategy did not require taking Rome. It required Rome's Italian allies to defect, leaving Rome isolated and forced to negotiate. Some did. Capua and much of the south went over. But the core of the Latin allies held, and Rome's willingness to keep raising new armies after losses that would have ended most states did not break.

Rome then adopted the approach associated with Fabius Maximus: refuse battle, shadow the Carthaginian army, attack its foraging parties, retake the cities that had defected. Hannibal could not force a decision against an enemy that declined to be decisive.

Meanwhile Rome fought elsewhere. Scipio took Carthaginian Spain, removing Hannibal's recruiting base. In 207 BCE Hannibal's brother Hasdrubal crossed the Alps with reinforcements and was intercepted and destroyed at the Metaurus before the two armies met.

The End

In 204 BCE Scipio landed in Africa. Carthage recalled Hannibal to defend the city, ending sixteen years in Italy. At Zama in 202 BCE the two commanders met, and Scipio, who had studied Cannae carefully, had the better cavalry and used it the way Hannibal once had.

Carthage lost its fleet, its territories outside Africa, and the right to make war without Roman permission. Fifty years later Rome destroyed it entirely.

Hannibal's reputation survived his defeat because his problem was structural. He beat every Roman army he met in open battle and still lost, because Rome could replace armies and Carthage could not replace him.