The Romans had not been unaware of their great foe Hannibal’s audacious plan to cross the Alps. Ever since the Carthaginian had crossed the Ebro River in 218 BC, the Romans had heard rumours about the commander’s daring intent to bring the Second Punic War to Italy, the heartlands of Roman power. Nevertheless, the speed with which Hannibal acted caught the Romans completely by surprise.
They had hoped to confront Hannibal at the Rhône river, far to the west of Italy in Gaul. Yet much to their dismay, their Punic foe successfully evaded them, having pushed ahead towards the Alps without hesitating. Hannibal was determined to fight this war on his field of choosing, not Rome’s.
News of Hannibal’s arrival in northern Italy in November 218 BC therefore caught the Romans off-guard. Not only did they have no idea of where exactly Hannibal’s army was marauding, but most of their troops were still lodged in their winter barracks.
The Battle of the Ticino River: November 218 BC
Near the Ticino River, Hannibal and his army came face to face with their foe. The Roman army under the command of Publius Cornelius Scipio, the Roman consul of 218 BC, was sizeable, believed to be around 20,000 men strong. Yet the result of this initial clash proved anticlimactic. It ended up being little more than a cavalry skirmish. But it was the Roman cavalry that came off worse in this melee. Scipio himself was among those who suffered in the fighting, rescued from certain death by the heroics of his son, also called Publius. Scipio retreated with his army south, across the Trebia River. It was first blood to Hannibal.
Much of Cisalpine Gaul was now at the mercy of Hannibal’s army. Two major Celtic tribes in the region, the Insubres and the Boii, were already favourable to Hannibal’s conquest. His victory at the Ticino quickly convinced the rest of the region’s Celtic tribes to follow suit. His army doubled in size, the manpower lost while crossing the Alps replaced by ferocious Celtic warriors. These weer some of the most renowned fighters in the Mediterranean.
Meanwhile, as Hannibal was making progress in northern Italy, to the south in Sicily another Roman force, under the command of Tiberius Sempronius Longus, had been preparing its own expedition. Following in the footsteps of generals Agathocles and Pyrrhus, Longus and his army were getting ready to set sail from Sicily and invade Africa with a large army. They sought to strike directly at Carthage, the heart of the Carthaginian Empire. But when news of the defeat at the Ticino River arrived, the plan was altered completely.
Seeing Hannibal as the most pressing threat, Longus was ordered north to reinforce Scipio. The invasion of Africa was put on hold; it would remain so for the next 14 years.
What happened at the battle of the Trebia?
Longus and his army of over 25,000 men reached his fellow consul on the eastern bank of the Trebia River in December 218 BC. Hannibal’s army was close by, encamped opposite the Romans on the western bank. Longus, assuming command of the army as Scipio was injured, believed he could defeat the Carthaginians in a pitched battle on open plains. But Hannibal was prepared: he would fight this war on his own terms.
Early one morning, Hannibal put his plan into action. He sent his elite Numidian cavalry, lightly-armed with javelins and swift mounts, to raid the Roman encampment. He hoped to lure the Romans across the icy river to its western bank. Longus quickly retaliated, sounding the advance. He had taken the bait.
Crossing the river
Without breakfast the Roman foot-soldiers began to wade through the icy river – first the lighter troops, the velites, and followed up by the heavy infantry, the principes. By the time they had reached the far side of the Trebia, its cold waters had severely sapped their energy. Now they had to fight.
Meanwhile the Roman cavalry had been hopelessly pursuing their Numidian counterparts. Overstretched and exhausted from the chase, they soon gave up and returned to the Roman line now forming up on the western bank of the Trebbia. Yet there would be no respite for the shivering Romans. As Longus’ velites began to reform in front of the army, Hannibal’s swift Numidian cavalry came charging in, breaking their ranks.
Calamity on the Trebia
Seeing his skirmishers being slaughtered, Longus ordered them to pull back. Now was the time, he thought, to send forwards his heavy infantry, his principes, and crush Hannibal’s battle line. It was all or nothing. The result was calamity. As these heavily-armed footmen advanced, Hannibal’s Numidian cavalry continued to prove their worth. Seeing an opportunity, these versatile light cavalry troops, along with Hannibal’s elephants, descended on the exhausted Roman cavalry positioned on either flank, routing them completely.
Stripped of support, fatigued and suffering from hypothermia, the principes now found themselves in dire straits. Any chance of them confronting Hannibal’s main battle line had evaporated. Already, the battle of the Trebia was turning into an unmitigated disaster for the Romans. But the worst was yet to come.
The night before, Hannibal had sent his younger brother, Mago, with a detachment of troops to encamp by the south-west side of the river. Until this stage of the battle, Mago’s troops had been lurking from an unseen vantage point. But when they saw the velites retreating and the principes drawing closer to Hannibal’s main battle line, they made their move. Breaking from cover, they ambushed the vulnerable flanks of the Roman heavy infantry and trapped the velites on the western bank. A massacre ensued. Hannibal emerged victorious.
Though having just gained a stunning victory, Hannibal was forced to regroup before he could continue the offensive and plunge into the heart of Italy. For the next three months, he would thus remain in northern Italy, awaiting the spring. For the Romans, the respite was welcome news. It provided them with precious time – time in which they were able to muster four new legions and reorganise the remnants of Scipio’s and Longus’ armies. Replenished, they once again planned to confront the Carthaginian menace.