Battle of the Trebia

The approximate extent of territory controlled by Rome and Carthage immediately before the start of the Second Punic War.

The First Punic War was fought between Carthage and Rome: the 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 also in North Africa.[23] The war lasted for 23 years, from 264 to 241 BC, until the Carthaginians were defeated.[24][25] The Treaty of Lutatius was signed by which Carthage evacuated Sicily and paid an indemnity of 3,200 talents[note 4] over ten years.[27] Four years later Rome seized Sardinia and Corsica on a cynical pretence and imposed a further 1,200 talent indemnity.[note 5][28][29] The seizure of Sardinia and Corsica by Rome and the additional indemnity fuelled resentment in Carthage.[30][31] Polybius considered this act of bad faith by the Romans to be the single greatest cause of war with Carthage breaking out again nineteen years later.[32]

Shortly after Rome's breach of the treaty the leading Carthaginian general Hamilcar Barca led many of his veterans on an expedition to expand Carthaginian holdings in south-east Iberia (modern Spain and Portugal); this was to become a quasi-monarchial, autonomous Barcid fiefdom.[33] Carthage gained silver mines, agricultural wealth, manpower, military facilities such as shipyards and territorial depth; which encouraged it to stand up to future Roman demands.[34] Hamilcar ruled as a viceroy and was succeeded by his son-in-law, Hasdrubal, in the early 220s BC and then his son, Hannibal, in 221 BC.[35] In 226 BC the Ebro Treaty was agreed, specifying the Ebro River as the northern boundary of the Carthaginian sphere of influence.[36] A little later Rome made a separate treaty with the city of Saguntum, well south of the Ebro.[37] In 219 BC a Carthaginian army under Hannibal besieged, captured and sacked Saguntum.[38][39] In spring 218 BC Rome declared war on Carthage.[40]

It was the long-standing Roman procedure to elect two men each year, known as consuls, to each lead an army.[41][42] 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 Cisalpine Gaul (modern northern Italy), antagonised by the founding of several Roman settlements on traditionally Gallic territory, attacked the Romans, capturing several towns. They repeatedly ambushed a Roman relief force and blockaded it in Tannetum.[43] 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.[44]

Hannibal's route from Iberia to Italy

Meanwhile, Hannibal assembled a Carthaginian army in New Carthage (modern Cartagena) over the winter, marching north in May 218 BC he entered Gaul to the east of the Pyrenees, then took an inland route to avoid the Roman allies along the coast.[45][46] 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 (modern Marseille) 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.[47][48][46] 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;[49][50] Publius returned to Italy.[50] The Carthaginians crossed the Alps with 38,000 infantry and 8,000 cavalry[45] in October, surmounting the difficulties of climate, terrain[45] and the guerrilla tactics of the native tribes.[51]

Hannibal arrived with 20,000 infantry, 6,000 cavalry and an unknown number of elephants – the survivors of the 37 with which he left Iberia[52][53] – in what is now Piedmont, northern Italy. The Romans had already withdrawn to their winter quarters and were astonished by Hannibal's appearance.[54] The Carthaginians needed to obtain supplies of food, as they had exhausted theirs during their journey, and obtain allies among the north-Italian Gallic tribes from which they could recruit, in order 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, (near the site of modern Turin) stormed it, massacred the population and seized the supplies there.[55][56] The modern historian Richard Miles believes that with these brutal actions Hannibal was sending out a clear message to the other Gallic tribes as to the likely consequences of non-cooperation.[57]

Cisalpine Gaul in 218 BC, depicting the Gallic revolt and the Carthaginian invasion

Hearing that Publius Scipio was operating in the region, he assumed the Roman army in Massala which he had believed en route to Iberia had returned to Italy and reinforced the army already based in the north.[note 6] 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.[59][58] 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.[60]

After camping at Placentia (modern Piacenza), a Roman colony founded earlier that year,[note 7] the Romans created 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.[61] 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.[62][63] Scipio mixed a large force of velites (javelin-armed light infantry) with his main cavalry force, anticipating a large-scale skirmish.[62][64][65][66] Hannibal put his close-order cavalry in the centre of his line, with his light Numidian cavalry on the wings.[64][67]

A Carthaginian cavalryman of Hannibal's army, as depicted in 1891

On sighting the Roman infantry the Carthaginian centre immediately charged and the javelinmen fled back through the ranks of their cavalry.[68] A large melee ensued, with many cavalry dismounting to fight on foot and many of the Roman javelinmen reinforcing the fighting line.[69][70] This continued indecisively until the Numidians 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.[68][62] The Romans broke and fled, with heavy casualties.[71][64] Scipio was wounded and only saved from death or capture by his 16-year-old son, also named Publius Cornelius Scipio.[68] That night Scipio broke camp and retreated over the Ticinus; the Carthaginians captured 600 of his rearguard the next day.[69]

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 8 kilometres (5 mi) away.[72] 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.[25][73] 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.[72] 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.[74][75] 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.[76]

Detail from the Ahenobarbus relief showing two Roman foot-soldiers from the second century BC

Most male Roman citizens were eligible for military service and would serve as infantry, a better-off minority providing a cavalry component. Traditionally, when at war the Romans would raise two legions, each of 4,200 infantry[note 8] and 300 cavalry. Approximately 1,200 of the infantry, poorer or younger men unable to afford the armour and equipment of a standard legionary, served as javelin-armed skirmishers, known as velites; they carried several javelins, which would be thrown from a distance, a short sword, and a 90-centimetre (3 ft) shield.[89] The balance were equipped as heavy infantry, with body armour, a large shield and short thrusting swords. They were divided into three ranks, of which the front rank also carried two javelins, while the second and third ranks had a thrusting spear instead. Both legionary sub-units and individual legionaries fought in relatively open order. An army was usually formed by combining a Roman legion with a similarly sized and equipped legion provided by their Latin allies; allied legions usually had a larger attached complement of cavalry than Roman ones.[41][42]

The combined force which Sempronius led into battle included four Roman legions. At full strength these should have mustered 16,800 men, including 4,800 velites; at least one of the legions is known to have been significantly understrength. Polybius gives a total of 16,000 Romans, Livy 18,000. In addition there were approximately 20,000 allied infantry, comprising four Latin allied legions and a strong force of Gauls. Mention is made of 6,000 light infantry and it is unclear whether these are included in the 36,000, or 38,000, infantry or in addition to them. As the nominal total number of velites from eight legions is 9,600, and it is known that many were lost at the Battle of the Ticinus, most modern historians assume that the 6,000 are included within the total number of infantry given. There were also 4,000 cavalry, a mixture of Romans, Latin allies and Gauls.[90]

Carthage usually recruited foreigners to make up its army. Many would be from North Africa (often referred to as "Libyans") which provided several types of fighters including: close-order heavy infantry equipped with large shields, helmets, short swords and long thrusting spears; javelin-armed light infantry skirmishers; close-order shock cavalry (also known as "heavy cavalry") carrying spears; and light cavalry skirmishers who threw javelins from a distance and avoided close combat (these were usually Numidian).[91][81] Iberia provided large numbers of experienced infantry; unarmoured troops who would charge ferociously, but had a reputation for breaking off if a combat was protracted.[92][93] The close-order North African infantry would fight in a tightly packed formation known as a phalanx and were well trained and disciplined.[81] Slingers were recruited from the Balearic Islands.[94][95] The Carthaginians also famously employed the war elephants which Hannibal had brought over the Alps; North Africa had indigenous African forest elephants at the time.[note 9][93][97] The sources are not clear as to whether they carried towers containing fighting men.[98]

Hannibal had arrived in Italy with 20,000 infantry and 6,000 cavalry.[52][99] At Trebia this had grown to 29,000 infantry – 21,000 close-order and 8,000 light infantry – and 11,000 cavalry. In each case they would be a combination of Africans, Iberians and Gauls; the proportions in each case are not known, other than that 8,000 of the close-order infantry were Gauls. In addition there were the elephants – the survivors of the 37 with which he left Iberia.[100]

The terrain between the Carthaginian camp and the Trebia was a unwooded flood plain, where it was apparently impossible to stage an ambush.[67] Hannibal however, had Mago (a Carthaginian general and one of Hannibal's younger brothers) take 1,000 cavalry and 1,000 infantry during the night to the south of where he intended to fight the battle and secret themselves in an old watercourse full of brush.[101]

The next morning, either 22 or 23 December, was cold and snowy. Shortly before daybreak Hannibal sent his Numidian cavalry across the river to force back the Roman pickets and provoke a fight. Meanwhile the rest of his army ate an early breakfast and prepared for battle. When the Numidians appeared Sempronius ordered out all of his cavalry to chase them off. Polybius writes "the Numidians easily scattered and retreated, but afterwards wheeled round and attacked with great daring—these being their peculiar tactics."[102] When the confrontation broke down into a wheeling mass of cavalry, but with the Numidians refusing to withdraw, Sempronius promptly ordered out first his 6,000 velites and then his whole army. He was so eager to give battle that few, if any, of them had eaten breakfast. The Numidians withdrew slowly and Sempronius pushed his whole army after them, in three columns, each 4 kilometres (2.5 mi) long, through the icy waters of the Trebia, which was running chest-high. The Romans were met by the Carthaginian light infantry, with behind them the entire Carthaginian army forming up for battle. The Romans also organised themselves in battle formation and advanced.[103][104]

  Carthaginians

  Romans

	Locations	Comments
1	Carthaginian camp	Exact location unknown
2	Carthaginian cavalry	10,000: 5,000 on each wing
3	Carthaginian infantry	20,000 heavy infantry, with 8,000 light infantry to their front, who fell back to the wings
4	Mago Barca's detachment	1,000 infantry, 1,000 cavalry
5	Trebbia river	Approximation only
6	Roman cavalry	4,000: 2,000 on each wing
7	Roman infantry	36,000: 16,000 Romans; 20,000 Latin allies and Cenomani Gauls – of these 30,000 were heavy infantry
8	Roman camp	Sempronius' camp. Scipio's camp was further upstream.
9	Po river	Approximation only
0	Approcimate location of Placentia	Modern Piacenza

The cavalry fell back to their positions on the wings. The large number of light infantry in each army – entirely javelinmen for the Romans, a mixture of javelinmen and slingers from the Balearics for the Carthaginians – skirmished between the main armies. The Roman velites had used many of their javelins against the Carthaginian cavalry, while the Carthaginian skirmishers were fully supplied; as opposed to their opponents, the velites were unfed, and also tired and cold from having forded the Trebia; and the slingers among the Carthaginians outranged the velites by some distance. For these reasons the Carthaginians got the better of the initial skirmishing and drove the velites back through the gaps in their supporting heavy infantry. The Carthaginian light infantry then moved towards the flanks of their army and harassed the Roman cavalry with their missiles, before finally falling back behind their own cavalry as the gap between the armies closed.[90]

The Carthaginian army formed up symmetrically: the 8,000 Gallic infantry were in the centre; on each side of them was a formation of 6,000 African and Iberian veteran infantry; on the far side of each of these were half of the surviving elephants; and on each wing were 5,000 cavalry. The Romans too formed up symmetrically: the Roman heavy infantry were in the centre, perhaps 13,000 strong; on each side of them were part of their allied force, some 17,000 in total – this included a large force of Cenomani Gauls, but the sources are unclear as to how many or where they were positioned. The survivors of the 6,000 velites were regrouping to their rear. Like the Carthaginians, the Romans divided their 4,000 cavalry between their wings.[83]

The Romans had a total of approximately 30,000 heavy infantry to the Carthaginians' 20,000 and could expect sooner or later to overwhelm their opponents by weight of numbers. The Carthaginian line was also in danger of being outflanked by the stronger Roman force; to guard against this Hannibal thinned the Carthaginian line, especially that of the Gauls in the centre, to be able to lengthen it to match the Romans'. Also, with tactical forethought typical of him, he had positioned the elephants on either side of the infantry, which discouraged the Roman infantry from approaching their flanks too closely.[105]

On each wing 5,000 Carthaginian and 2,000 Roman cavalry charged each other. The Roman cavalry were not only outnumbered, but their horses were tired from chasing the Numidian cavalry and many had been wounded by the fire of the Carthaginian light infantry.[83] Both encounters ended rapidly, with the Romans fleeing back over the Trebia, and most of the Carthaginian cavalry pursuing them. Goldsworthy describes the fight put up by the Roman cavalry as "feeble",[106] while the military historian Philip Sabin says that the two contests were "speedily decided".[82] The Carthaginian light infantry, who had withdrawn to the wings behind the cavalry, moved forward and round the now exposed Roman flanks. The Roman light infantry, who had withdrawn to the rear of Roman heavy infantry, turned to face this developing Carthaginian threat.[106] Many of the Roman allied heavy infantry on each flank also turned to their flanks to face this new threat; this inevitably took much of the impetus out of their parent formation's push against the African and Iberian infantry to their fronts.[107]

Roman statuette of a war elephant recovered from Herculaneum

At the same time, unnoticed in the heat of battle, Mago's force of 2,000 had been making its way down the watercourse, and then onto the plain and into a position where they could attack the Romans' left rear. While all this was happening, the fighting between the two heavy infantry contingents had continued fiercely, with the more numerous and better armoured Romans getting the better of it; despite being weakened by many of their component units having to turn to the flank or rear.[107] Mago's force charged into the velites who were already fending off the Carthaginian light infantry, but their formation held. Increasing numbers of Carthaginian cavalry broke off their pursuit, returned and attacked the Roman rear. Eventually the strain told and the units of Latin allies and Gauls on the flanks and the velites to the rear started to break up.[105]

Meanwhile, the Roman infantry in the centre routed the 8,000 Gauls facing them, as well as a unit of African heavy infantry, and broke clean through the centre of the Carthaginian army. By the time they halted their pursuit and reorganised it was clear the rest of their army behind them had dissolved and that the battle was lost. Sempronius, who was fighting with the Roman infantry, ordered them away from the site of the battle and, maintaining their formation, 10,000 of them re-crossed the Trebia and reached the nearby Roman-held settlement of Placentia without interference from the Carthaginians. The Carthaginians concentrated on pursuing and cutting down the partially-surrounded balance of the Roman army.[108]

There is debate among modern historians as to the Roman losses. Dexter Hoyos states that the only Roman survivors were the infantry who broke through the Carthaginian centre.[109] Richard Miles says that "many" not in this group were killed;[110] although Nigel Bagnall writes that this was only a minority of the Roman cavalry.[111] Adrian Goldsworthy states that the Romans "suffered heavily", but that "numbers of soldiers" straggled into Placentia or one of their camps in addition to the formed group of 10,000;[112] while John Lazenby argues that in addition outside of the 10,000, "few" infantry escaped, although "most" of the cavalry did;[113] as does Leonard Cottrell.[114] According to Paul Erdkamp, the Romans lost 20,000 killed during the battle, half of their force; this excludes those captured.[115]

Carthaginian losses are generally agreed to have been several thousand of the Gallic infantry in the centre, a smaller number of his other infantry and of his cavalry; and several elephants.[113][111][109]