Marcus Atilius Regulus had been winning. After the Roman naval victory at Cape Ecnomus -- possibly the largest naval battle in history, with some 680 warships and up to 290,000 men engaged -- Regulus landed in Africa and waged a devastating campaign. His forces captured 20,000 enslaved people, seized vast herds of cattle, and took the city of Aspis on the Cape Bon Peninsula. When most of the Roman fleet and army returned to Sicily, Regulus pressed inland with just 15,000 infantry and 500 cavalry. He defeated the Carthaginians at the Battle of Adys, captured Tunis only 16 kilometers from Carthage, and watched as Carthage's African subjects revolted. The capital filled with refugees. Food ran short. Carthage sued for peace. Regulus, convinced he faced a broken enemy, offered terms that amounted to total subjugation: surrender Sicily, Sardinia, and Corsica; limit the navy to a single warship; pay tribute forever. The Carthaginians found these terms completely unacceptable and decided to fight on.

Among a fresh batch of mercenary recruits arriving from Greece was Xanthippus, a Spartan trained in the military methods for which his city was famous. He quickly identified the problem that had plagued every Carthaginian army facing Rome: they were fighting on the wrong terrain. Carthage's greatest military assets were its cavalry and war elephants -- North Africa still had indigenous forest elephants at the time -- but every recent engagement had taken place on hills, behind fortifications, or in broken terrain where these advantages were nullified. Xanthippus convinced the Carthaginian Senate that battles needed to be fought on open, level ground. He was given charge of training the army over the winter, and as his skill became evident, full operational command followed. Whether this transfer of authority came from the Senate, the generals, or the rank-and-file troops is unclear. What is clear is that Xanthippus transformed a demoralized army into a disciplined force.

Xanthippus marched out of Carthage with 100 elephants, 4,000 cavalry, and 12,000 infantry, setting up camp on an open plain near Tunis -- exactly the terrain he had advocated for. Regulus advanced with his 15,000 infantry and 500 cavalry, camping two kilometers away. The next morning, Xanthippus deployed his elephants in a single line before the infantry center, with cavalry equally divided on the flanks. Regulus responded by packing his legionaries into a deeper, denser formation than usual -- a reasonable anti-elephant tactic, but one that fatally shortened his front line, making it vulnerable to being outflanked. The battle opened with the Carthaginian cavalry sweeping the hopelessly outnumbered Roman horsemen from the field. Part of the Roman left wing overlapped the elephant line and routed the Carthaginian right, pursuing them back to camp. But the rest of the Roman infantry collided with the elephants, which charged home despite the legionaries' shouting and shield-banging.

Disordered by the elephants, some Roman legionaries fought their way through to attack the Carthaginian phalanx but were too disorganized to break it. Then the Carthaginian cavalry returned from its pursuit and began striking the Roman flanks and rear. Trapped, the dense Roman formation became a killing field. When Xanthippus ordered the phalanx forward, most of the legionaries could not even raise their weapons. Regulus and 500 survivors were captured after fighting their way out of the encirclement, only to be run down. About 2,000 Romans from the left wing escaped to Aspis. Regulus died in Carthaginian captivity; later Roman authors invented stories of his heroic endurance as a prisoner. Rome sent a fleet to evacuate its survivors and won a naval battle at Cape Hermaeum, capturing 114 Carthaginian ships. But on the return voyage, a storm sank 384 Roman ships and killed an estimated 100,000 men, mostly non-Roman allies. The war ground on for another 14 years before Rome finally prevailed.