The Battle of the Saw was the culminating battle of a campaign fought between a Carthaginian army led by Hamilcar Barca and a rebel force led by Spendius in 238BC in what is now northern Tunisia. Carthage was fighting a coalition of mutinous soldiers and rebellious African cities in the Mercenary War which had started in 241BC. The rebels had been besieging Carthage while the Carthaginian field army under Hamilcar raided their supply lines. Under this pressure the rebels pulled back to their base at Tunis and despatched their own army to prevent Hamilcar's activities and, ideally, destroy his army.
Unable to confront the Carthaginian war elephants and cavalry on open ground, the rebels stayed on higher and rougher terrain and harassed the Carthaginian army. After several months of campaigning, the details of which are not clear in the sources, Hamilcar trapped the rebels in a pass or against a mountain range. 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. Eventually, the surrounded troops forced their leaders to parley with Hamilcar, but he took all of them prisoner. The Carthaginians then attacked the leaderless, starving rebels with their whole force, led by their elephants, and massacred them to a man.
The rebel leaders were crucified in sight of their comrades in Tunis. A little later the rebels abandoned Tunis and withdrew south. Hamilcar and fellow general Hanno followed and in late 238BC wiped them out at the Battle of Leptis Parva.
Background
The First Punic War was fought between Carthage and Rome, the two main powers of the western Mediterranean in the 3rd centuryBC, and lasted for 23 years, from 264 to 241BC. The two powers struggled for supremacy primarily on the Mediterranean island of Sicily and its surrounding waters, and also in North Africa. After immense materiel and human losses on both sides, the Carthaginians were defeated and their commander on Sicily agreed the Treaty of Lutatius.
During the last years of the war with Rome, the Carthaginian general Hanno the Great was leading a series of campaigns which greatly increased the area of Africa controlled by Carthage. Hanno was rigorous in squeezing taxes out of the newly conquered territory to pay for both the war with Rome and his own campaigns. Half of the area's agricultural output was taken as war tax, and the tribute previously due from towns and cities was doubled. These exactions were harshly enforced, causing extreme hardship in many areas.
Mutiny
Following the Carthaginian defeat by the Romans, their army of 20,000 men on Sicily was evacuated to Carthage. Rather than promptly paying the several years' back pay they were owed and hurrying them home, the Carthaginian authorities decided to wait until all of the troops had arrived and then attempt to negotiate a settlement at a lower rate. 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. Eventually they forcibly took over the city of Tunis. Panicking, the Carthaginian Senate agreed to payment in full. This seemed to have abated the discontent when, suddenly, discipline broke down. 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.
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. The pay dispute had become a full-scale revolt. The three years of war that followed are known as the Mercenary War and threatened Carthage's existence as a state.