The Battle of Trebia took place on December 18, 218 B.C., near the banks of the Trebia River, in the Italian province of Emilia, in which the Roman general Tiberius Sempronio Longo was defeated by the Carthaginian army commanded by Hannibal, in one of the most important warlike successes of the Punic Wars where Romans and Carthaginians clashed.
Sick from injury and shaken by the defection of the Gauls, Publius Cornelius Scipio was determined not to engage in combat against the Carthaginian until he was joined by his fellow consul, Sempronius. The latter, having put his legionaries under oath to return to Arimino (now Rimini) as quickly as they could (a terrifying march from the southern end of the Italian Peninsula to the northeast, on the Adriatic coast, in some forty days), was now in a position to cross his two legions through Placencia. Scipio, however, instead of staying in the garrisoned city, decided, according to Polybius, to “raise camp and march toward the River Trebia.” He hoped to find in the hills around the river a safer place in which to camp and hold off the Carthaginians until he received reinforcements.
Hannibal couldn”t miss the news of this troop deployment; as soon as Publius Cornelius Scipio began his retreat, he sent his Numidians to follow the Romans on their march. This was the moment when Scipio would surely have been drawn into battle and utterly destroyed. The Numidians, however, unable to resist the temptation to raid and plunder, set aside the pursuit and, having plundered the remains of the Roman camp, set fire to it. Although some of his rearguard were killed or captured, Scipio managed to establish himself in a solidly fortified camp along the small hills above the river. Hannibal would not go after him. When the battle came, it would be on his own terms; he had no intention of leading his troops across the Trebia to meet, on the other side, an already entrenched Roman army. In the meantime, a bit of good luck came his way: the nearby citadel of Clastidio, used as a supply depot by the Romans, was betrayed by its commander (by a large bribe, Livy says), and its granary served the Carthaginians well when the northern winter of the Italian Peninsula set in. Rain, frost, freezing winds, and the surrounding land becoming more and more muddy – these were the conditions both sides faced as the year came to an end.
Sempronio now moved through Arimino (now Rimini) and joined Publius Cornelius Scipio. Although his army had marched from Sicily and from there had crossed almost the entire length of the Italian Peninsula – an excellent testament to Roman endurance and discipline – it was still relatively strong. Unlike Scipio”s troops, badly beaten during the Gaulish uprising and already hit by the first blows of the Carthaginians, Sempronio and his men, prepared as they were for the attack on Carthage, could hardly wait for contact with the enemy. This was especially true for Sempronio himself, an ambitious man, particularly eager to fight before his consular period expired. The fact that Scipio was almost completely out of action because of his injury meant, in practice, the transfer of command into Sempronio”s hands; however, the weakness of the system – the divided command – undoubtedly compromised the entire Roman reaction to Hannibal”s presence in the region. Scipio was in favor of procrastination, of waiting through the winter, keeping Hannibal in trouble but not involving themselves in serious conflict, until the more acceptable climate of the new year set in – when, too, they would be reinforced by Rome. Sempronio judged that, with his two consular armies united and counting the forces of his Latin and Gaulish allies, there were more than enough men in number to take on the Carthaginian forces without much risk. The weather was more hostile to the Carthaginians than to the Romans – accustomed as they were to such winters – and although Hannibal”s troops had been reinforced by the Gauls, they would hardly be in good condition so immediately after crossing the Alps.
With this gathering, just before the battle of Trebia, the consular forces numbered about sixteen thousand Romans, added to twenty thousand allies and four thousand horsemen. Hannibal”s army was smaller – consisting of twenty thousand infantrymen among Africans, Iberians and Celts, while his cavalry, including Celtic allies, numbered about ten thousand. Hannibal consequently had a more numerous cavalry, but his infantry was inferior in quantity, and most of his men were far from their best physical condition. It is almost certain that each side had a fairly accurate estimate of its enemy”s strength, for the Gauls who passed between the lines – some pro-Roman, some pro-Cartaginian – must have brought their input to the officers of both armies. Nevertheless, it is likely that Hannibal”s information system was better, since a greater number of Gauls were inclined to act in favor of the Carthaginians. He also maintained, from the first days he planned his campaign, a very efficient espionage system in the Italian Peninsula. It is unlikely that he was unaware of the differences between the two consuls, and that he did not weigh the fact that Sempronio was in effective command – particularly when the armies were approaching battle – and Publius Cornelius Scipio, unfit to go into the field. It was on Sempronio”s well-known ambition and desire for swift victory that he had to base his entire strategy.
Looking for a pretext to act, Sempronio was not slow to find one. Hannibal was concerned that a number of Gauls in the region between the Trebia and the Po River were trading with both the Romans and the Carthaginians, striving to profit from the impending conflict. He then dispatched two thousand infantrymen and a thousand horsemen to raid their land, hoping to frighten them inside the Carthaginian camp, and also to provoke a Roman response. This was not long in coming, for when the Gauls came to the Romans for help, Sempronio immediately sent most of his cavalry and a thousand infantrymen.
Once they crossed the Trebia, they entered into combat with Hannibal”s invading party; a tumultuous minor combat ensued, in which the Romans were superior. Such skirmishing had the desired effect; as Polybius reports “Tiberius (Sempronius), exalted and full of joy at his success, was all anxiety to fight a decisive battle as soon as possible.” The advice of Publius Cornelius Scipio, namely, that it would be better to wait for his legions to improve their performance with winter exercises, and to count on the fact that the Celtic infidels would soon desert Hannibal, was ignored. Sempronio “was eager to strike the decisive blow himself and did not wish Scipio to be present at the battle, or for the consuls appointed to take office before it was all over – and that moment was now at hand.”
Everything was happening according to Hannibal”s designs, and his view of the situation was similar to that of Scipio. The Romans would certainly do better to wait, but he wanted action quickly – while Sempronio remained in effective command, while his own Gauls still looked forward to the battle, and before the Romans had more time to train their inexperienced, as yet untested troops in battle. On the morale of Hannibal”s men, Polybius wisely remarks that, “when a general brings his army into a foreign country and is engaged in an enterprise of such risk, his only source of security consists in keeping the hopes of his allies constantly alive.
Like all great generals, Hannibal knew how to make the land work in his favor. Trained since childhood in camps, and since his youth in war, he had assimilated a special knowledge of space, density, and configuration of the land around him, a rare characteristic that distinguished him from other military men. He had noticed, during his inspection of the territory between his own camp on the western side of the Trebia and the river, a small watercourse with steep banks and dense bushes and thickets. At first glance, it would go unnoticed, especially in the rain and opaque winter light. It lay south of his camp, south of the plain across which any army would have to pass to attack him. If Hannibal could lure the Romans across the Trebia, by placing his own troops north of this place “well suited for an ambush,” then it would be possible to hide troops in the area who would just wait until the enemy had passed to attack him from the rear. Polybius, with his military experience, comments: “Any watercourse with a narrow bank and reeds or ferns (…) can be used not only for concealing infantrymen, but also dismounted horsemen, sometimes taking care to place the shields with very visible details within the ground protrusions and to hide the helmets under them.
Hannibal now possessed a war council. He knew that Sempronio, especially since his small success over the Carthaginian invading party, was ready and eager to fight. He only needed a little encouragement – a new incursion, perhaps, but this time in his own camp. With his aggressive confidence, the Roman consul would never be able to tolerate a reckless gesture like an attack on the Roman camp itself. Everything depended on the success of the ambush. Hannibal selected his younger brother Magno – eager to earn his spurs – and put him in command of a chosen force of a thousand infantrymen and a thousand horsemen. Magno”s orders were to leave the camp after dark, take up position in the bushes around the small ravine, and stay there in hiding until he judged the moment to be opportune. Hannibal then explained exactly his plan for the main action.
At dawn the next day, all the Numidian horsemen carrying light weapons crossed the Trebia and, in the opaque morning light, would make an attack on the Roman camp. Their part in the day”s work was very important, and Hannibal promised them appropriate rewards if they achieved the result he expected. As soon as the Romans woke up and began to react to the marauding horsemen”s arrows and spikes, they retreated, but not before giving the enemy time to mount their horses and ride off in pursuit. The goal was to draw not only the Roman cavalry, but the entire army across the Trebia into the flat land where Hannibal”s troops would be positioned for battle.
Sempronio, as soon as the Numidians fell upon his camp, immediately dispatched his own cavalry to fight them. It could have amounted to no more than a skirmish, with the Numids leaving as soon as the heavy cavalry arrived; but the consul had taken the bait. Determined to inflict the Carthaginians a severe defeat – or even more – he sent six thousand infantrymen armed with azagayas and set about moving the entire army. “It was,” as Livy tells us, “a day of terrible weather (it was snowing in the region between the Alps and the Apennines, and the proximity of rivers and marshes intensified the bitter cold. By sending out his Numidians at first light in the morning, Hannibal had ensured that the Romans, surprised without having had a morning meal, would be forced to hurry, unprepared and still half asleep. His own men, however, forewarned and well-informed, calmly made their breakfast, stood in front of fires for warmth, and braced their bodies against the cold, wind and frost. The horses received food and water, and were groomed and prepared; the elephants were also cared for, as they would be used at the head of the cavalry on each flank of the army, to provide protection for their own riders. For Hannibal, that would be a special battle, a model of care and elaboration that he would reminisce about in the years to come.
The Romans, in their stubborn and characteristic bravery, formed up and headed toward the river. Here Hannibal made the forces of nature work for him: “At first their enthusiasm and eagerness sustained them, but when they had to cross the flooded Trebia due to the rain that had fallen during the night upriver (…) the infantry had great difficulty in crossing, with the water at breast height. Polybius continues: “The result was that the whole force suffered greatly from the cold and also from hunger as the day progressed.
Hannibal waited without attempting any attack until the Romans crossed the river, and only then did he order about eight thousand spearmen and slingers to attack the enemy while he remade his formation. The Balarid spearmen, with their deadly accuracy, hit the soldiers as if they were birds on the ground, as the flow of water broke the line formation; the spearmen, dressed in light clothing, selected and shot individual targets and stabbed them into the ground, while they themselves remained out of the cutting and piercing range of the Roman glades. This thin, short sword had its merits when used by soldiers in a disciplined line, but was disadvantaged in individual combat.
Moving calmly as the advancing forces shattered the Romans as soon as they formed ranks, Hannibal”s troops had time to position themselves almost as if for a ceremonial parade. For that day”s operation, Hannibal allowed a long line of infantry: carrying heavy weapons, the Africans and Iberians served as reinforcements for the Gauls; the cavalry, on each flank, with the elephants and their drivers emerging in front of the riders – a frightening sight under the cold, overcast winter skies. Sempronio, as we read, “advanced against the enemy in imposing style, marching neatly at a slow pace.”
The troops armed with light weapons began the battle, but even here the Carthaginians had the upper hand, for the Romans had expended most of their throwing shells against the wild first attack of the Numidians. As soon as the light forces retreated between the gaps left in the ranks for them, the first clash of heavy infantry occurred. As the cores entered combat, the Carthaginian cavalry directed their attacks to both flanks of the enemy, vigorously investing for the assault and possessing numerical superiority. The Roman wings began to give way, and as they did so, the Numidian light horsemen and Carthaginian spearmen, following their own heavy cavalry, took advantage of the weak point left on each flank of the Roman infantry.
As both cores engaged in hand-to-hand combat, the Roman cavalry retreated and their infantry on each flank began to collapse. Hannibal”s trap was activated. Emerging from their hiding places in the rain-hidden ravine behind the Romans, Magnon and his special force attacked with great momentum to hit the enemy”s core from the rear. Barreling through the falling hail, the elephants helped drive back the wing, which, plagued by the Numids and other light troops, began to fall into the turbulent, icy river behind it.
The Roman legionnaires in the vanguard, with their flanks exposed and their rear under attack, fought valiantly and broke through the narrow Carthaginian ranks. Ten thousand of them managed to hold their disciplined formation and retreat to Placencia.
It is thought to have been a remarkably organized retreat, with an efficient rearguard fighting the pursuing Carthaginians, so that they still managed to cross the Trebia again and reach the city that served as their garrison (something Livy neglects to mention). The rest of the Roman army, both cavalry and infantry, dispersed in ragged groups amidst the Carthaginian advance and the sudden attack by Magog Barca and his men from the rear. Most of those who did not die in the field were slaughtered while trying to cross the voluminous river; those who escaped joined the general retreat toward Placencia. The Carthaginians were wise and – no doubt on Hannibal”s orders – did not attempt to pursue the enemy beyond the river line.
Strategy and tactical planning triumphed that day. The Romans were disoriented, and their armies in pieces or scattered in flight. Thousands of Romans and their allies had been killed and thousands became prisoners. The road south through the Apennines was open to the invader. Something the battle had somehow demonstrated – the failure of its own core in the face of Roman penetration – must have suggested to Hannibal a stratagem he would employ in the future, on the distant field of Canas. Most of the casualties in his troops were among the Gauls, possibly because of their wild and undisciplined attacks, or because they were not as well protected by body armor as the Carthaginians. Hannibal would see to correcting this defect by carefully training his new troops and distributing among them shields, helmets and armor collected from the captured Romans. Heavy losses had occurred among the elephants – Polybius states that all but one were killed, and Livy says “almost all” – but this only demonstrated their incompatibility with the terrain and climate of the Italian peninsula.
An attempt was made by the Romans, particularly by Sempronio, to disguise the nature of their defeat by asserting that their army had only been prevented from winning by the violence of the weather. The real state of affairs could not be concealed for long, for the Carthaginians were still encamped; the Gauls, hesitant as to their future alliance, joined Hannibal without any objection, and the remnants of the two consular armies beat a retreat to Placencia and Cremona. The news that Hannibal had crossed the Alps resounded in Rome; the cavalry conflict at Ticino had been like the first and decisive beat of an ominous drum roll; but the defeat of two consular armies at Trebia did not sound like a murmur of thunder in the distant hills, but like the deep rumble of an advancing avalanche that would shake Rome to its foundations.