Carthage and Rome fought through the First Punic War primarily for supremacy in North Africa and on the Mediterranean island of Sicily and in its surrounding waters.

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.

As Atillius neared Tannetum, the Gauls retreated without a fight,[42] and the Romans spent the summer of 218 BC recovering and fortifying Placentia and Cremona, probably in a two-month-long operation.

Hannibal's passivity and non-threatening defensive dispositions during March through May[45][46] probably influenced this decision by reinforcing the Roman perception that they were fighting a repeat of the first war and the initiative lay with them.

[18] Hannibal's overland approach to Italy was a high-risk strategy, and failure might have cost Carthage the war,[54] but he was forced to choose this option given the strategic limitations the Carthaginian empire faced in 218 BC, and it had a chance of succeeding.

[55] An overland invasion would have the advantage of surprise[31] while sailing to Italy might have been faster and safer from hazards of a land march, but Roman naval dominance[56][note 3] increased the risk to Hannibal's armada,[note 4] of crippling losses from Roman naval attacks despite Carthaginian warship escorts, and ships could also be lost in storms en route to Italy.

[71] After the successful conclusion of the Siege of Saguntum, Hannibal did nothing to provoke the Romans, dismissed his army, and did not immediately march for Italy in the spring of 218BC after he received the news of the war.

[21][note 6] Hannibal left Cartagena in late May or early June,[80] timing his departure to allow the spring flooding of Spanish rivers to subside.

[92] The main column under Hannibal, along with the treasure chest and elephants, crossed the Ebro at the town of Edeba[91] and proceeded directly along the coast through Tarraco, Barcino, Gerunda, Emporiae and Illiberis.

A general named Hanno, who has been identified by various authors as Hannibal's nephew[98] (son of Hasdrubal the Fair), a brother,[99] or no Barcid relation, garrisoned the newly conquered territory north of the Eboo with 10,000 infantry and 1,000 cavalries and based himself to specifically watch over the Bargusii, a pro-Roman tribe.

[112][note 8] Hannibal had sounded out the Volcae, the Salyes and the Allobroges regarding safe passage for Carthaginian arms during before he departed from Iberia,[115] and had enlisted the cooperation of the Boii and Insubres of Po valley to ensure provisions and reinforcements awaited him after crossing the Alps when he was at his most vulnerable point.

[120] The tribes were divided over granting Carthaginians safe passage,[121] and as the Carthaginians regrouped, the Gauls mustered their forces and their leaders met at Ruscino for discussion, Hannibal met and placated the Gallic chieftains with assurances of his peaceful intentions accompanied by generous gifts, then marched past Ruscino unmolested,[94] and probably marched along with the future Via Domitia towards Nemasus, the Volcae capital, and without any incidents reached the west bank of the Rhône by late September.

[122] Hannibal's negotiation skills and war chest was put to good use to placate individual Gallic tribes on the way,[61] so the foraging of the Carthaginians caused no friction, supplies may also have been purchased from the Gauls[123] as no reports exist of any fighting taking place during his march.

[136][127][24] Hannibal put Hanno, son of Bomilcar, in charge of a mobile column made up of infantry and cavalry on the third night, before starting the boat building, and sent this force north upriver under cover of darkness to find another suitable crossing place.

[136][127] The leadership qualities of Hanno and the skill and discipline of the Carthaginians are evident from the fact that they had managed to pull off this whole operation undetected and unobserved by the Gauls, which was crucial to its success.

[158] The Gauls were brave, fierce warriors who fought in tribes and clans in massed infantry formation, but lacked the discipline of their Roman and Carthaginian opponents.

The Infantry wore no armor, fought naked or stripped to the waist in plaid trousers and a loose cloak, a variety of metal bossed different size and shaped shields made of oak or linden covered with leather[159] and iron slashing swords.

[127] Hannibal had planned 1,000 yard river crossing carefully, having spent five days analyzing this dangerous operation from every angle, ensuring that as little as possible was left to chance.

Assuming a 12–16 kilometres (7.5–9.9 mi) march limit per day for the Carthaginian army, the site is likely between Avignon and Orange, upstream of the Durance river, based on the probable ancient coastline, which has advanced further south because of silting from the Rhône since 218 BC.

[169] While Hannibal was engaged crossing the Rhone, Publius Scipio, who could not set out from Rome before late August or early September, two to three months behind schedule[109] due to raising fresh levies from scratch to replace the troops sent to Cisalpine Gaul, had arrived on the Rhône estuary.

[171] Scipio knew that Hannibal had crossed the Ebro before he sailed and had assumed that the Carthaginians were still engaged beyond the Pyrenees,[172] so he disembarked his troops, made camp, unloaded his heavy baggage, and allowed his soldiers to recuperate from their sea voyage.

Hannibal, unaware of the Roman scouts bearing down on him, began to ferry his troops, pack animals, and baggage across using the boats, rafts, and canoes in relays, by nightfall most of the army except the elephants had crossed over and a camp was firmly established.

[180] Hannibal learned that a Roman Army and fleet had arrived at the mouth of the Rhône, probably from the Gallic envoys who had come from the Po valley,[181] on the day after the battle.

[135] Hannibal dispatched 500 Numidian horses immediately on a scouting mission to the south, then held a troop review and harangued his men, and introduced Magilus,[182] and some other Gallic chiefs of the Po valley to his soldiers.

[182] The Numidians blundered into a force of 300 Roman cavalries from the army of Publius Cornelius Scipio and a contingent of Gallic mercenaries hired by Massalia[184] a few miles south of the camp.

[188] Hannibal had considered fighting Scipio, but ultimately had decided to march for Italy across the Alps, as a brilliant tactical victory might lead to a strategic defeat by forcing him to winter in Gaul.

8,000 horse and 37 elephants against 46,000 foot and 4600 horse)[191] and he was vastly superior in the cavalry arm and was confident of victory,[192] however, his soldiers were tired from the recent battle and river crossing,[181] battle casualties would diminish his numbers and the wounded would slow down his march, and the delay might force him to winter in Gaul,[193] risking Gallic attacks on his weakened army and running short of supplies, as Hannibal was dependent on foraging.

[202] It is known that Hannibal took an estimated four to five weeks to cross the Alps, faced harsh conditions and attacks from Gallic tribes, losing up to 20,000 soldiers and the majority of his pack animals[204] before he reached Italy.

[208] He tried to persuade the Taurini to join him, and failing that, attacked their chief town, took it after a three-day siege, and put the survivors to the sword, securing provisions for his army and Gauls now began to rally to him.

The cause of this drastic reduction is speculated as: large scale desertion by recruits,[96] high casualties suffered north of the Ebro from direct assaults on walled towns,[97] garrisoning of parts of Gaul,[222] severe winter conditions faced on the Alps, and the unreliability of the figures given by Polybius.