The middle of Rome's three Punic Wars (264–146 BCE), the Second Punic War, staged one of antiquity's most striking demonstrations of personal command. In the autumn of 218 BCE, Hannibal Barca set out from his base in Hispania with a large army and several dozen elephants and marched through the Pyrenees, Gaul, and finally the Alps into northern Italy. The crossing was extraordinarily costly, but striking Rome from the north neutralized Roman naval superiority.

In the following years Hannibal won a sequence of major battles in Italy: Trebia (218 BCE), Trasimene (217), and Cannae (216). His double-envelopment of two consular armies at Cannae remains one of the most studied actions in military history; it stands as the greatest battlefield loss Rome ever suffered. Yet Rome did not surrender. Most allied cities held; new legions were levied; Fabius Maximus's strategy of harassment and delay avoided pitched battles. For fifteen years Hannibal stayed in Italy without the siege capability to take the city itself.

The war was decided in Spain (Scipio Africanus's campaigns) and then in North Africa: Scipio's invasion forced Hannibal back to defend Carthage and led to the battle of Zama (202 BCE), where Scipio defeated Hannibal. The peace the next year stripped Carthage of its standing as a Mediterranean power. The Third Punic War (149–146) ended in Carthage's complete destruction. The Second Punic War's true legacy is not any single battle but Rome's consolidation as a land power and the opening of an unbroken path to Mediterranean dominance.