Pinned against the mountains, their supply lines blockaded and with their food exhausted, the rebels ate their horses, their prisoners and then their slaves, hoping that their comrades in Tunis would sortie to rescue them.

[8][9] Freed of their long period of military discipline and with nothing to do, the men grumbled among themselves and refused all attempts by the Carthaginians to pay them less than the full amount due.

Several soldiers insisted that no deal with Carthage was acceptable, a riot broke out, dissenters were stoned to death, the Senate's negotiators were taken prisoner and their treasury was seized.

[10][11][12] Spendius, an escaped Roman slave who faced death by torture if he were recaptured, and Mathos, a Berber dissatisfied with Hanno's attitude towards tax-raising from Carthage's African possessions, were declared generals.

The news of an experienced, anti-Carthaginian army in the heart of Carthage's territory spread rapidly and caused many cities and towns to rise in rebellion.

Provisions, money and reinforcements poured in; eventually another 70,000 men joined the anti-Carthaginian movement, according to the ancient historian Polybius, although many would have been tied down in garrisoning their home towns against Carthaginian retribution.

It included deserters from the rebels, 2,000 cavalry, and 70 elephants, and was placed under the command of Hamilcar Barca,[note 1] who had previously led the Carthaginian forces on Sicily.

He was shadowed by a larger rebel force under Spendius, which kept to rough ground for fear of the Carthaginians' cavalry and elephants, and harried his foragers and scouts.

[28] Since leaving Carthage, Hamilcar had treated rebels he had captured well and offered them a choice of joining his army or free passage home.

Encouraged by his senior subordinates, notably the Gaul Autaritus, to remove the possibility of any goodwill between the sides, he had 700 Carthaginian prisoners tortured to death: they had their hands cut off, their legs broken, were castrated, and were thrown into a pit and buried alive.

[26][29] At some point between March and September 239 BC the previously loyal cities of Utica and Hippo slew their Carthaginian garrisons and joined the rebels.

[29] In early 238 BC the lack of supplies forced Mathos to lift the close siege of Carthage; he maintained a more distant blockade from Tunis.

Roman sources refer to these foreign fighters derogatively as "mercenaries", but the modern historian Adrian Goldsworthy describes this as "a gross oversimplification".

[note 3][38] The rebel field army which commenced the campaign is estimated to have been about 50,000 strong, leaving the 20,000-man balance of their force to continue blockading Carthage from their stronghold of Tunis.

The Carthaginians were probably organised in three divisions: one under Hamilcar, one under his senior subordinate general Hannibal,[note 4] and the third a strong cavalry force commanded by Naravas.

[41] The rebels succeeded in driving off Hamilcar's force, and so opened up a route for supplies to reach both themselves and their comrades in Tunis, but the primary sources do not state how this was accomplished.

[44] The primary sources give a confusing account of the subsequent months-long campaign of manoeuvre, with ambushes, traps, stratagems and much marching and counter-marching.

[46] Broadly this was to the rebels' advantage, if they could keep their army intact the Carthaginian strength would shrink; they had no need, nor desire, to risk a pitched battle.

He had been almost continuously in command of an army for a decade, while the rebel generals had at best experience as junior officers – Spendius was an escaped slave turned ordinary soldier.

Hoyos suggests that the rebels had relaxed their guard in a supposedly secure area believing that they had broken contact with the Carthaginians, but that Naravas's skilled scouts identified their location.

By the time they had grasped the situation the Carthaginian army had fortified itself in positions where the terrain was what Polybius describes as "unhelpful" to the rebels and any attack by them was clearly hopeless.

Hamilcar took Spendius, Autaritus, Zarzas and their lieutenants prisoner[56] and the Carthaginians then attacked the leaderless, starving rebels with their whole force, led by their elephants.

The city was difficult to access from both the east and the west, so Hamilcar occupied a position to the south with half the army, and his deputy Hannibal was to the north with the balance.

[57] Hanno and Hamilcar marched after the rebels with an army totalling over 25,000 men and many war elephants,[62] including every Carthaginian citizen of military age.