Hannibal's crossing of the Alps in 218 BC was one of the major events of the Second Punic War, and one of the most celebrated achievements of any military force in ancient warfare.

After the Carthaginians' loss of the war, the Romans imposed terms that were designed to reduce Carthage to a tribute-paying city to Rome and simultaneously strip it of its fleet.

It was the ambition of the Barcas, one of the leading noble families of the patriotic party, to establish the Iberian peninsula as a base of operations for waging a war of revenge against the Roman military alliance.

Those two factors went together, and in spite of conservative opposition to his expedition, Hamilcar set out in 238 BC[10][11][12] to begin his conquest of the Iberian peninsula with these objectives in mind.

[17] These colonies expressed concern about the consolidation of Carthaginian power on the peninsula, which Hasdrubal's deft military leadership and diplomatic skill[14] procured.

Hannibal spent the first two years of his command seeking to complete his father's ambition while simultaneously putting down several potential revolts that resulted in part from the death of Hasdrubal, which menaced the Carthaginian possessions already conquered thus far.

[20] During the next two years, Hannibal reduced all of Iberia south of the Ebro to subjection, excepting the city of Saguntum, which, under the aegis of Rome, was outside of his immediate plans.

Seeing an opportunity for a triumph for themselves, the consuls Marcus Claudius and Gnaeus Cornelius vigorously rejected the embassy, and the Gauls prepared for war with the Romans.

Polybius had this to say about Hannibal's plans:Conducted his enterprise with consummate judgement; for he had accurately ascertained the excellent nature of the country in which he was to arrive, and the hostile disposition of its inhabitants towards the Romans; and he had for guides and conductors through the difficult passes which lay in the way of natives of the country, men who were to partake of the same hopes with himself[38]These preparations being completed, Hannibal sought to induce the Saguntines to come to arms with him and thereby declare war on Rome through her proxy.

After receiving route information from his scouts and messages from the Celtic tribes that resided around the Alps, Hannibal set out with 90,000 heavy infantry from various African and Iberian nations, and 12,000 cavalry.

Massalia feared the arriving Carthaginian army, and sought to influence the native tribes on the eastern bank of the Rhône to take up the cause of the Romans.

However, modern historians agree on where Hannibal encamped his army on the western bank of the Rhône and see the river crossing as clearly conceived and crisply executed.

[53] Upon the arrival of intelligence indicating the presence of the Carthaginians in the neighbourhood of Massalia, the consul gave up his proposed Iberian expedition and instead redirected his efforts to prevent Hannibal's crossing of the Rhône.

[63] There can be no doubt that Hannibal knew of Alexander the Great's crossing of the Hydaspes river in India as, from a tactical and strategic standpoint, he employed almost the same strategy.

[64][65][63] However, some were put on boats fully saddled and ready for immediate use,[64] so that, once they debouched from the river, they could cover the infantry and the rest of the army while it formed up to attack the barbarians.

Often during this period, to intimidate their enemy, troops would be ordered to pound their shields with their weapons and raise loud cries at precisely the same moment to create the greatest amount of noise.

While the actual conflict took a short time, Hannibal had spent five days preparing this risky operation, ensuring that it was ready and as little as possible was left to chance.

In addition, they were negligent about their order of march,[70] and early Roman history records many massacres of consular armies by other nations because of their lack of proper precaution against these.

[66][72] Hannibal's purpose was to inspire his men with confidence in the planned expedition by showing them Padane Gallic chieftains who offered them their aid.

[73] Not knowing that the Romans were ultimately going to set out for Italy, when his cavalry had crossed the river he ordered them to curtain his march on his southern flank, towards the sea.

The events recorded in ancient accounts, and their relationship to the Alpine geography, have been a matter of historiographical dispute since the decades following the Second Punic War.

[82] Biostratigraphic archaeological data has reinforced the case for Col de la Traversette; analysis of peat bogs near watercourses on both sides of the pass's summit showed that the ground was heavily disturbed "by thousands, perhaps tens of thousands, of animals and humans" and that the soil bore traces of unique levels of Clostridia bacteria associated with the digestive tract of horses and mules.

Mahaney et al. argue that factors used by De Beer to support Col de la Traversette including "gauging ancient place names against modern, close scrutiny of times of flood in major rivers and distant viewing of the Po plains" taken together with "massive radiocarbon and microbiological and parasitical evidence" from the alluvial sediments on either side of the pass furnish "supporting evidence, proof if you will" that Hannibal's invasion went that way.

Virtually all of these barbarians died in the ensuing combat, as they were fighting with their backs to a steep precipice, trying to throw their arrows and darts uphill at the advancing Carthaginians.

[88] After this contest of arms, the baggage was held together in good order and the Carthaginian army followed the road down to the plain that begins roughly at modern Bourget.

Hannibal then addressed his army, and we are informed that they were made to appreciate the extent of the effort they were about to undergo and were raised to good spirits in spite of the difficult nature of their undertaking.

It was the end of October and snowy weather, the length of the campaign, ferocity of the fighting, and the loss of animals sapped morale in the army's ranks.

[98] According to Polybius,[99] Hannibal assembled his men, declared to them that the end of their campaign was drawing near; and pointed to the view of Italy, showing his soldiers the Po Valley and the plains near it, and reminded them they had been assured of Gallic friendship and aid.

If, however, Hannibal had ascended the Col de la Traversette, the Po Valley would indeed have been visible from the pass's summit, vindicating Polybius's account.

[103] Hannibal attempted to detour by marching through a place where there was a great deal of snow – the Alps' altitude at this point retains snowpack year around.