Battle of the Trebia
The Battle of the Trebia was the first major battle of the Second Punic War, fought between the Carthaginian forces of Hannibal and a Roman army under Sempronius Longus on 22 or 23 December 218 BC. Each army had a strength of about 40,000 men; the Carthaginians were stronger in cavalry, the Romans in infantry. The battle took place on the flood plain of the west bank of the lower Trebia River, not far from the settlement of Placentia, and resulted in a heavy defeat for the Romans.
War broke out between Carthage and Rome in 218 BC. The leading Carthaginian general, Hannibal, responded by leading a large army out of Iberia, through Gaul, across the Alps and into Cisalpine Gaul. The Romans went on the attack against the reduced force which had survived the rigours of the march, and Publius Scipio personally led the cavalry and light infantry of the army he commanded against the Carthaginian cavalry at the Battle of Ticinus. The Romans were soundly beaten and Scipio was wounded. The Romans retreated to near Placentia, fortified their camp and awaited reinforcement. The Roman army in Sicily under Sempronius was redeployed to the north and joined with Scipio's force. After a day of heavy skirmishing in which the Romans gained the upper hand, Sempronius was eager for a battle.
Hannibal used his Numidian cavalry to lure the Romans out of their camp and onto ground of his choosing. Fresh Carthaginian cavalry routed the outnumbered Roman cavalry and Carthaginian light infantry outflanked the Roman infantry. A previously hidden Carthaginian force attacked the Roman infantry in the rear. Most of the Roman units then collapsed and most Romans were killed or captured by the Carthaginians, but 10,000 under Sempronius maintained formation and fought their way out to the safety of Placentia. Recognising the Carthaginians as the dominant force in Cisalpine Gaul, Gallic recruits flocked to them, and Hannibal's army grew to 60,000. The following spring, it moved south into Roman Italy and gained another victory at the Battle of Lake Trasimene. In 216 BC Hannibal marched to southern Italy and inflicted the disastrous defeat of the Battle of Cannae on the Romans, the last of what modern historians describe as the three great military calamities suffered by the Romans in the first three years of the war.
Background
Pre-war
The First Punic War was fought from 264 to 241 BC between Carthage and Rome: these two main powers of the western Mediterranean in the 3rd century BC struggled for supremacy primarily on the Mediterranean island of Sicily and its surrounding waters and in North Africa. The war lasted for 23 years until the Carthaginians were defeated. Five years later an army commanded by the leading Carthaginian general Hamilcar Barca landed in Carthaginian Iberia which he greatly expanded and turned into a quasi-monarchical, autonomous territory ruled by his family, the Barcids. This expansion gained Carthage silver mines, agricultural wealth, manpower, military facilities such as shipyards and territorial depth, which encouraged it to resist future Roman demands.Hamilcar ruled Carthaginian Iberia autonomously until his death in 228 BC. He was succeeded by his son-in-law, Hasdrubal and in 221 BC by his son Hannibal. In 226 BC the Ebro Treaty established the Ebro River as the northern boundary of the Carthaginian sphere of influence in Iberia. A little later Rome made a separate treaty of association with the independent city of Saguntum, well south of the Ebro. In 219 BC a Carthaginian army under Hannibal besieged, captured and sacked Saguntum, which led Rome to declare war on Carthage.
War in Cisalpine Gaul
It was the long-standing Roman procedure to elect two men each year as senior magistrates, known as consuls, who in time of war would each lead an army. In 218 BC the Romans raised an army to campaign in Iberia under the consul Publius Scipio, who was accompanied by his brother Gnaeus. The major Gallic tribes in the area of north Italy either side of the River Po known as Cisalpine Gaul were antagonised by the settling of Roman colonists at Piacentia and Cremona earlier that year on traditionally Gallic territory. They rose and attacked the Romans, capturing several towns. They repeatedly ambushed a Roman relief force and blockaded it in Tannetum. The Roman Senate detached one Roman and one allied legion from the force intended for Iberia to send to the region. The Scipios had to raise fresh troops to replace these and thus could not set out for Iberia until September.Carthage invades Italy
Meanwhile, Hannibal assembled a Carthaginian army in the Iberian city of New Carthage in late 219 and early 218 BC. This marched north in May 218 BC, entering Gaul to the east of the Pyrenees, then taking an inland route to avoid Roman allies along the coast. Hannibal left his brother Hasdrubal Barca in charge of Carthaginian interests in Iberia. The Roman fleet carrying the Scipio brothers' army landed at Rome's ally Massalia at the mouth of the River Rhone in September, at about the same time as Hannibal was fighting his way across the river against a force of local Allobroges at the Battle of Rhone Crossing. A Roman cavalry patrol scattered a force of Carthaginian cavalry, but Hannibal's main army evaded the Romans and Gnaeus Scipio continued to Iberia with the Roman force; Publius returned to Italy. The Carthaginians crossed the Alps with 38,000 infantry and 8,000 cavalry in October, surmounting the difficulties of climate, terrain and the guerrilla tactics of the native tribes.Hannibal arrived with 20,000 infantry, 6,000 cavalry and about 30 war elephants from the force with which he had left Iberia in what is now Piedmont, northern Italy. The Romans had already withdrawn to their winter quarters and were astonished by Hannibal's appearance. The Carthaginians needed to obtain supplies of food, as they had exhausted theirs during their journey. They also wanted to obtain allies among the north-Italian Gallic tribes from which they could recruit, to build up their army to a size which would enable it to effectively take on the Romans. The local tribe, the Taurini, were unwelcoming, so Hannibal promptly besieged their capital, stormed it, massacred the population and seized the supplies there. With these brutal actions Hannibal was sending out a clear message to the other Gallic tribes as to the likely consequences of non-cooperation.
Hearing that Publius Scipio was operating in the region, Hannibal assumed the Roman army in Massalia, which he had believed en route to Iberia, had returned to Italy and reinforced the army already based in the north. Believing that he would therefore be facing a much larger Roman force than he had anticipated, Hannibal felt an even more pressing need to recruit strongly among the Cisalpine Gauls. He determined that a display of confidence was called for and advanced boldly down the valley of the Po. However, Scipio led his army equally boldly against the Carthaginians, causing the Gauls to remain neutral. Both commanders attempted to inspire the ardour of their men for the coming battle by making fiery speeches to their assembled armies. Hannibal is reported to have stressed to his troops that they had to win, whatever the cost, as there was no place they could retreat to.
First contact
After camping at Placentia the Romans constructed a pontoon bridge across the lower River Ticinus and continued west. With his scouts reporting the nearby presence of Carthaginians, Scipio ordered his army to encamp. The Carthaginians did the same. Next day each commander led out a strong force to personally reconnoitre the size and make-up of the opposing army, things of which they would have been almost completely ignorant. Scipio mixed a large force of velites with his main cavalry force, anticipating a large-scale skirmish. Hannibal put his close-order cavalry in the centre of his line, with his light Numidian cavalry on the wings.On sighting the Roman infantry the Carthaginian centre immediately charged and the javelin-men fled back through the ranks of their cavalry. A large mêlée ensued, with many cavalry dismounting to fight on foot and many of the Roman javelin-men reinforcing the fighting line. This continued indecisively until the Numidian cavalry swept round both ends of the line of battle and attacked the still disorganised velites, the small Roman cavalry reserve to which Scipio had attached himself, and the rear of the already engaged Roman cavalry, throwing them all into confusion and panic. The Romans broke and fled, with heavy casualties. Scipio was wounded and only saved from death or capture by his 16-year-old son, also named Publius Cornelius Scipio. That night Scipio broke camp and retreated over the Ticinus; the Carthaginians captured 600 of his rearguard the next day.
The Romans withdrew as far as Placentia. Two days after this clash the Carthaginians crossed the River Po and marched towards Placentia. They formed up outside the Roman camp and offered battle, which Scipio refused. The Carthaginians set up their own camp some away. That night 2,200 Gallic troops serving with the Roman army attacked the Romans closest to them in their tents and deserted to the Carthaginians, taking the Romans' heads with them as a sign of good faith. Hannibal rewarded them and sent them back to their homes to enrol more recruits. Hannibal also made his first formal treaty with a Gallic tribe and supplies and recruits started to come in. The Romans abandoned their camp and withdrew under cover of night. The next morning the Carthaginian cavalry bungled their pursuit and the Romans were able to set up camp on an area of high ground by the River Trebia at what is now Rivergaro, a little south west of Placentia. Even so, they had to abandon much of their baggage and heavier gear and many stragglers were killed or captured. Scipio waited for reinforcements while Hannibal camped at a distance on the plain on the other side of the river, gathering supplies and training the Gauls now flocking to his standard.