The battle of Adys was the first major battle during the Roman invasion of North Africa during the First Punic War. Having captured Aspis, a Roman army under the consul Marcus Regulus had moved inland, plundering. Reaching the walled town of Adys, they had settled down for a regular siege. Meanwhile, the Carthaginians had been convinced that the Romans would sail directly for Carthage and so had concentrated their efforts on defending the city. Learning of the Roman landing at Aspis, the Carthaginians began to create a field army to oppose them. Two generals - Bostar and Hadrubal son of Hanno – were appointed to command the troops already at Carthage (amongst them the survivors of the defeat at Cape Ecnomus), while Hamilcar was recalled from Sicily, along with a force of 5,000 infantry and 500 cavalry.
This army advanced towards the Romans around Adys. Polybius reports that its strongest elements were its cavalry and elephants, which were only effective on the plains. Despite this, the Carthaginian commanders decided to take up position on a hill overlooking the Roman position.
Regulus took advantage of the chance this gave him. Splitting his army into two, probably with one legion in each half, he launched a dawn attack on the Punic camp. On one flank the mercenaries fighting for Carthage launched a attack that forced one legion to give way, but in doing so they advanced off the hilltop. Regulus counterattacked with his second force, and retrieved the situation. The Carthaginian army was pushed out of its camp in some disarray.
Regulus was preventing from winning a crushing victory by his lack of cavalry, which probably allowed the Carthaginian cavalry and elephants to escape. The Punic infantry was chased for a short distance, while the Romans plundered their abandoned camp.
In the aftermath of the battle, Regulus moved to Tunis. The situation in Carthage was now desperate. The city was full of refuges from both the Roman invasion and Numidian raids. Hoping to gain a full victory before the end of his year of office, Regulus tried to negotiate a Carthaginian surrender. However his terms were considered unacceptably harsh (exactly what these terms were is no longer clear – the only source to give details is late and not always reliable). The Carthaginians decided to fight on, placing Xanthippus, a Spartan mercenary, in charge of their armies. Over the winter of 256-255 he was able to create an army that inflicted a heavy defeat on Regulus at the battle of Tunes.