On the first day of the Somme, in 1916, in an age of mechanized and mass mobilized warfare, the British army suffered a shocking 20,000 fatalities. This is well known. What is less well-known, is that over 2000 years earlier, in the era of sword shield and bow, the Republican Roman army lost as many as 50,000 dead in a single day against a smaller and lighter-equipped Carthaginian army. This battle, at Cannae, was the masterpiece of Hannibal Barca, and one of the most spectacular military victories of all time.
Few tales from history can match the epic grandeur of Hannibal’s march into Italy during the Second Punic War. It was set against the backdrop of two powers that had grown too big to share the central Mediterranean clashing through the 3rd and 2nd centuries BC. Carthage was a powerful maritime empire based around its capital of the same name which now lies in modern Tunisia. It predated Rome as a major power, and by the time of their first war in 264 BC Carthage controlled much of north Africa, Spain and the western part of Sicily. It was this last province that would cause it to come into contact with Rome, the city-state that had now come to dominate much of Italy after defeating the Greek states of Magna Grecia (southern Italy). The first war between the two powers (known as the First Punic War) was fought over Sicily, and was a see-sawing contest on land and at sea – a theater of war that the Carthaginians had previously dominated. In the end, the bloody-minded and determined Romans were victorious, much to the disgust of the Carthaginian commander Hamilcar Barca, who made his 9 year-old son Hannibal swear that as long as he lived, he would never be a friend of Rome.
After their defeat, the navy and finances of Carthage were in a sorry state, but Hamilcar was not done. Taking his sons with him, he lead an invasion of the Iberian Peninsula in order to subdue the hardy tribes that resisted Carthaginian rule. After the death of his father, the 26 year old Hannibal took command in 221 and immediately made a name for himself. His youth and energy made him popular with the multinational soldiers under his command, and a string of impressive victories helped subdue the Iberians and ensure that across the Balearic sea the Romans were paying close attention to the revival of the old enemy. The central government in Carthage had signed a peace treaty with Rome after their earlier defeat, but the Roman government declared an alliance with the independent Spanish city of Saguntum, knowing that Hannibal was planning on attacking it. The young commander was popular enough at this stage to take politics into his own hands, and marched to besiege the city anyway, perhaps thinking of his promise to his father. The government back in Africa had little choice but to support the decision, as a brutal eight-month siege ensued before Saguntum’s eventual bloody fall. Rome demanded an explanation for his actions and by 218 BC the two empires were once again at war, this time on a far greater scale. In the eyes of the Romans, they had already given Carthage one chance, this time it was all or nothing.
Hannibal’s reponse to the declaration of war was simple. He would continue his march north through Spain, all the way to the Alps, and then into Rome’s heartland. He had a 40,000 infantry, 8,000 cavalry and 38 war elephants by the time he’d reached the foothills, as well as boundless ambition. The crossing of the mountains in Spring was a disaster – costing him half his men and almost all of his war elephants. Most generals would have given up at this stage or at least limited their objectives, but Hannibal had a plan to attract Rome’s reluctant southern and northern subjects to his cause, and managed to win over the allegiances of many of the Alpine Gauls who had been troubling Rome with their raids for centuries. By the time of his first major battle with Rome at Trebia in December, his army was back up to 40,000 infantry (though they were not well-armoured like their Roman foes). He was still heavily outnumbered, but it did not seem to matter as the Romans were soundly defeated at Trebia and Lake Trasimene. This last victory took Hannibal deep into the fertile lands of Italy and put Rome into a state of blind panic. Had Hannibal struck at Rome then, history could have been very different, but he had no siege weapons and was still waiting for Roman allies to defect to even up the numbers. In these circumstances, Quintus Fabius was appointed an emergency dictator in Rome, and pursued a policy of attrition and refusing to meet the Carthaginians in a pitched battle. This managed to frustrate Hannibal for a year, but by 216 BC the people of Rome were growing angry. They wanted victory and this invader to be removed at any cost.
As a result, an army of unprecedented size had to be assembled. Some estimates are as high as 90,000 though 50-70 would be more likely. Even so, this was hugely impressive for a state still smaller than modern Italy in the ancient world, and dwarfed even the highest counts of Hannibal’s forces, which still numbered at about 40-50,000. Their enemy, meanwhile, was far to the south of Rome, attempting to court the former Greek city-states there, who they knew had little fondness for their conquerors. Hannibal had spent the winter and spring down in these balmy and fertile lands, and his own men had collected the harvest, meaning that they were well-fed and ready. Eager to take the initiative, he seized the important supply post at Cannae in the Spring, and waited for the Romans to come to him. They obliged. Two consuls, Varro and Paullus, commanded the Romans, and the accounts of ancient historians recount that Varro won a minor skirmish along the way to Cannae, which cultivated a dangerous sense of hubris in the days ahead. Though modern historians think that Varro’s fairly lowly origins made him something of a scapegoat for later writers, he still had every reason to be confident. He had more men, they were clad in heavy armour and fighting for their homelands, against a ragged army of Gauls Africans and Spaniards who were a very long way from home.
In ancient warfare the deployment of troops was crucial. The standard formation of the times was lines of lighter and then heavier infantry in the centre, with the cavalry protecting the flanks. Varro, however was wary of Hannibal’s genius and wanted to try something different. Conscious of one of Rome’s few successes in the war, which had been achieved by closely-packed heavy infantry, he made his men in the centre much closer together than was normal, creating a dense fist of armoured men which would smash through the weaker Carthaginian line. Hannibal meanwhile, placed his Spaniards and Iberians in the centre and veteran Africans on the flanks, meaning that to the Romans the task of breaking through the middle of the line and dividing the enemy army looked easy. The Carthaginian cavalry meanwhile, were placed opposite their Roman counterparts, and Hannibal knew that that would be where the battle could be won, rather than in the unequal clash of infantry.
This part of the battlefield was also where the fighting began. As the Roman infantry marched forwards, Hannibal’s horsemen – commanded by his brother Hasdrubal – engaged their counterparts and put them to flight after a brief and vicious struggle. This already left the slow-moving Roman infantry exposed, but the clouds of dust thrown up by so many thousands of men on a hot August day meant that they were oblivious to the danger. When they met the light Gallic and Spanish infantry in the centre, the Carthaginian general ordered them not to engage fully but to retreat steadily in the face of the closely-packed enemy who kept pressing further and further forwards, so enraged by the enemy refusing to stay put that they ignored the veteran Africans, who had remained in place and were now dangerously positioned on the flanks of the Romans.
As Varro’s men advanced further and further, the Africans began to press in on them, so that they were forced into a narrower and narrower corridor until they were so pressed together that they could barely swing their swords. Once their predicament reached this stage, Hannibal gave his Africans the fatal order to charge at the Roman flanks, completely encircling the Roman army and completing the pincer movement – one of the earliest in military history. Once the cavalry hit the Roman rear to complete the chaos, the battle ended as a contest. The slaughter, however, continued. Panicking, confused and hemmed in like cattle, thousands of Romans were massacred throughout the morning, with no means of escape with Carthaginians on all sides. Though some cut their way through to the nearest town, the vast majority of the massive army lay dead on the plain of Cannae, and Rome was in a state of numbed terror. Its survival seemed genuinely threatened.
Over a fifth of all Roman males over 17 had died in a single day. The old Greek cities, as well as King Phillip of Macedon, joined Hannibal after the defeat at Cannae. And yet Rome survived. Perhaps its reaction to Cannae is the best demonstration of why Romans came to rule the known world. Refusing to give in, they stopped risking all against Hannibal in open battle, formed new armies and ground him down with a scorched earth policy until he was forced to return to Africa in the face of a Roman invasion. The new hero of Rome Scipio Africanus, formed the nucleus od his army with the survivors of Cannae, who had been humiliatingly exiled to Sicily after their defeat, but won redemption at the decisively fought battle of Zama in 202 BC.
As a result, the reasons for the battle of Cannae’s enduring fame are not political ones, though it did form the climax of the romance of Hannibal’s doomed invasion of Italy. It did not topple Rome, or – ultimately – save Carthage from destruction at the hands of the newer power less than a hundred years later. However, it has been taught consistently in military academies ever since as the perfect way of destroying a superior force utterly using encirclement, and it has fascinated all the great commanders of modern times from Frederick the Great, to Napoleon, to Eisenhower, to said that “in modern war every ground commander seeks to duplicate the classic example of Cannae.”