Battle of the Rhône Crossing

The Battle of the Rhône Crossing was a battle during the Second Punic War in September of 218 BC. Hannibal marched on the Italian Alps, and an army of Gallic Volcae attacked the Carthaginian army on the east bank of the Rhône. The Roman army camped near Massalia. The Volcae tried to prevent the Carthaginians from crossing the Alps and invading Italy.

Before they crossed the river, the Carthaginians sent a detachment to cross upriver, under Hanno, son of Bomilcar, and took up position behind the Gauls. Once the detachment was in place, Hannibal crossed the river with the main contingent of his army. As the Gauls massed to oppose Hannibal, Hanno attacked their rear and routed the Volcae army. This was Hannibal's first major battle (victory) outside of the Iberian Peninsula. It gave him an unopposed path to the Alps and into Italy.

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. The war lasted 23 years, from 264 until 241 BC. It ended with the Treaty of Lutatius, under which Carthage evacuated Sicily and paid an indemnity of 3,200 talents over ten years. Four years later, Rome seized Sardinia and Corsica and imposed a further 1,200 talent indemnity. These seizures and the additional indemnity fuelled resentment in Carthage. Polybius considered this act of bad faith by the Romans as the single greatest cause of the war with Carthage breaking out again nineteen years later.

Shortly after the Roman breached the treaty, Carthaginian general Hamilcar Barca led many of his veterans to expand Carthaginian holdings in south-east Iberia (modern Spain and Portugal). 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. Hamilcar ruled as viceroy and was succeeded by his son-in-law Hasdrubal, in the early 220s BC and then his son Hannibal, in 221 BC. In 226 BC, the Romans and Carthaginians signed the Ebro Treaty, declaring the Ebro River the northern boundary of the Carthaginian sphere of influence. Rome later made a separate treaty with Saguntum, south of the Ebro. In 218 BC, a Carthaginian army under Hannibal besieged, captured and sacked Saguntum. In spring 219 BC Rome declared war on Carthage.

As Hannibal had anticipated, Rome expected the Carthaginians to fight a defensive war with minor attacks in Sicily, and therefore planned to attack both Spain and Africa. Understanding that a simultaneous strike against both Spain and Carthage at the earliest opportunity would give Hannibal the opportunity to defeat their armies in detail, they planned first for Scipio to engage Hannibal either north of the Ebro or east of the Pyrenées or the Rhône, where he could receive aid from allied Iberians or Gauls, and after Scipio had located and engaged Hannibal's forces, Sempronius, stationed in Sicily, would invade Africa.

Due to the size and defences of the city of Carthage, it would take the Romans months to starve the city out through siege and blockade. Additionally, relief armies would have to be beaten off during the siege. Since 241 BC, Rome had not negotiated but instead dictated terms to Carthage, which had always backed down. The Romans most likely expected that Carthage was bluffing when it refused to accept terms, and would capitulate as soon a Roman army blockaded the city, or roused the Numidians and Libyans to rebel against Carthage. Carthage came close to capitulation in 256–55 BC when Marcus Atilius Regulus invaded Africa. If Scipio could keep Hannibal away from Africa for long enough, perhaps Sempronius could repeat the feat, or the opponents of the Barcids, some of whom had relations with Roman senators might assume power, or trigger the recall of Hannibal, and accept Roman demands.

The Roman navy had been mobilized in 219 BC, fielding 220 quinqueremes for the Second Illyrian War. It was the long-standing Roman procedure to elect two men each year, known as consuls, to each lead an army, and Rome in 218 BC decided to raise two consular armies and strike simultaneously at Iberia and Africa.

Consul Tiberius Sempronius Longus received instructions to sail for Africa escorted by 160 quinqueremes, with four legions: two Roman legions and two allied legions consisting of 8,000 Roman and 16,000 allied infantry, and 600 Roman and 1,800 allied horses.