The Second Punic War was fought between Carthage and Rome from 218 to 204 BC. It was the second of three major wars fought between the Phoenician colony of Carthage, and the Roman Republic, then still confined to the Italian Penninsula.
After Carthage lost its holdings in Sicily to Rome in the First Punic War, Carthage moved to compensate for the loss by extending her territory in Iberia (the ancient Roman name for modern Spain and Portugal). This was began by Hamilcar Barca, and continued by his son-in-law Hasdrubal and then his son Hannibal. According to Roman tradition, Hannibal had sworn hatred to Rome, and he certainly did not take a conciliatory attitude when the Romans berated him for crossing the river Esbro, which they were by treaty required to stay south of. Asked to hand Hannibal over Carthage refused and so Rome declared war on Carthage.
The War in Italia
Hannibal took a combined army of 40,000 North Africans and Iberians across southern France and crossed the Alps over the winter. His invasion of Italia (the ancient Roman name for Italy) came as a surprise to the Romans, for he had constructed no fleet, and it was believed his army could not possibly make it through the mountains. Indeed, it sustained very heavy casualties, including all but one of his 37 war elephants. Nevertheless, that spring he came into North Italia with a still-formidable force of 26,000 men. The Romans tried to attack him while he was still unready, but he defeated them in a skirmish at the river Ticinus, and then again at the Trebia, where both the Roman consuls were killed along with a quarter of their forces. The Romans then pulled out, leaving Hannibal in command of North Italia. His support from the Gallic tribes and Italian cities was not what he had hoped for, but even so, he was able to strengthen his army to a force of 50,000 men.
The next year the Romans elected Gaius Flaminius consul in hopes that he could defeat Hannibal, and he set up an ambush at Arretium. However, Hannibal was warned of the attack and so by-passed the army, allowing him a free march on Rome. Flaminius had to pursue him but found himself ambushed at lake Trasimene, and was utterly defeated. However Hannibal, despite the urgings of his generals, did not proceed to besiege Rome, as he lacked siege equipment and he had no supply base in central Italia. Instead he proceeded to the non-Italian south in hopes of stirring up rebellion.
Meanwhile the veteran Fabius Maximus had been appointed Roman dictator, and he decided that it would be best to try and avoid any further field battles, instead trying to cut off Hannibal's supplies by devastating the countryside and harassing his army. Such operations are now called Fabian tactics after him, and earned him the nickname of the Cunctator (delayer), but were hated at Rome, and the following year he was replaced by two consuls who promised to end the war quickly. These jointly fielded the largest Roman army ever, which met Hannibal at Cannae (216). The Romans outnumbered the Carthaginians 50,000 to at most 40,000, but by allowing his center to retreat Hannibal was able to encircle their forces, and completely annihilated them. It is said that under a hundred Romans escaped.
The battle of Cannae led to some of the support Hannibal had hoped for. Over the next three years Capua, Syracuse, and Tarentum each went over to his side. Philip V of Macedonia also allied with Hannibal in 217 BC, starting the First Macedonian War against Rome, but his fleet was not able to stand up to Rome's and he was never able to give any useful help. Meanwhile the Romans had re-elected Fabius Maximus as dictator and returned to his delaying tactics, dividing their army into small forces at vital locations, and avoiding Carthaginian attempts to draw them into field battles.
The War in Iberia
While all this was happening, the Romans had carried the war into Iberia, and over the years had gradually expanded along the coast until in 211 BC they captured Saguntum. This prevented Hasdrubal from sending his brother any aid and also diverted Carthaginian reinforcements away from Italia. That same year they also recaptued Capua and Syracuse, the second falling after what was now a two-year siege, made famous by the defense engines made by Archimedes, who was killed in the sack of the city. However, Hasdrubal was able to defeat them in battle and the two Roman commanders, brothers named Publius and Cnomus Scipio, were killed. Even so he did not feel confident enough to expel their army after the other losses.
Next year the Romans sent out Publius Scipio's son and namesake, the future Scipio Africanus (though only 25 years old) and not having held any offices, with the authority of a consul. Vowing to avenge his father and uncle, he proceeded directly to what was effectively the capital of Punic Iberia, Carthago Nova. It fell in 209 BC, and Hasdrubal was deprived of the main port. He then decided to aid Hannibal in defeating Rome in Italia, and abandoning Iberia to some relatively weak garrisons set out to repeat his brother's crossing of the Alps. It did not work. This time, the Romans anticipated the army's arrival, and had two legions waiting for it when it arrived. Hasdrubal was defeated and killed, and the first news Hannibal received that he left Iberia came in the form of his head, flung into his encampment by a Roman horseman.
The Carthaginian forces that remained in Iberia were defeated a few years later, at Ilipa (206), and Iberia became a Roman province. In that time Rome had recovered Tarentum, and thanks to continual attrition and lack of support Hannibal's army had been confined to the southmost part of Italia. Macedonia had also withdrawn its support, feeling that the Carthaginian defeat was now only a matter of time.
The Attack on Carthage
Scipio returned to Rome a great hero, and though he was technically ineligible ran and was elected consul in 205 BC. He resolved to end the war by attacking Carthage itself, and appealed directly to the centurial assembly when he found the senate opposed this. Thus he was given command of the two legions in Sicily, plus 7,000 volunteers he had recruited, and the next year landed at Utica, about twenty miles away from Carthage. Here he was counting on support from the Numidians, who resented Carthaginian control and so agreed to provide him with cavalry. Hannibal was recalled from Italia, and had to leave the Iberian and Gallic contingents that made up about two-thirds of his army behind. After the loss of Capua he had begun to lose influence, but he was still able to break off peace talks, and Scipio met him at Zama in 202 BC. The infantry were evenly matched, and neither side was able to out-general the other, but the issue was decided when the Numidian cavalry dispersed the Carthaginian horsemen and was thus able to attack from behind. For this victory Scipio became known as Scipio Africanus. Carthage immediately sued for peace.
Iberia was lost to Carthage forever, and she was reduced to a client state. A war indemnity of 10,000 talents was imposed, her navy was limited to 10 ships to ward off pirates, and she was forbidden from raising an army without Rome's permission. Numidia took the opportunity to capture and plunder Carthaginian territory. Half a century later, when Carthage raised an army to defend itself from these incursions, it was destroyed by Rome in the Third Punic War.
Hannibal was one of the few survivors of the battle of Zama and escaped to the east, ending up at Antiochus' court in Syria. Rome feared him until the day he died, which was probably unwarranted, but together with Philip's attack on Italia resulted in great suspicion of the Hellenistic kingdoms, leading to further wars and eventually their conquest.