The siege of Acilla (January 46 BC) was an unsuccessful Republican attempt to recapture a city that had sided with Caesar after his arrival in North Africa.
In the aftermath of their defeat at Pharsalus (48 BC), many of the surviving Republican leaders fled to North Africa, where they were able to rebuild their strength while Caesar was trapped in Egypt. Eventually Caesar was free to turn his attention to North Africa, landing on the east coast of the Roman Province at the start of January 46 BC. A standoff soon developed between Caesar and Scipio around the city of Ruspina.
While Caesar and Scipio were engaged in the standoff outside Ruspina, a deputation from the nearby town of Acilla reached Caesar’s camp, offering to join his side if he would provide them with a garrison. Acilla was probably Acholla, a small city somewhere to the south of Ruspina. Caesar accepted their offer, and sent C. Messius, a former aedile, to take command of the city. He was given eight cohorts of Numidians and Getulians.
News of this offer quickly reached the Republicans. Considius Longus, the commander of the garrison at Hadrumentum. He had two legions and seven hundred cavalry under his command, and decided that he could afford to take eight cohorts to Acilla to attempt and stop Caesar’s men taking control of the city. However Messius moved quicker, and arrived before Longus, who was unwilling to risk a siege at this point. He then received extra cavalry from the main army, and with that reinforcement returned to Acilla and laid siege to the city.
The two sides were roughly equal in numbers. Longus appears to have constructed proper siege works, but after the siege had gone on for some time these were destroyed by the defenders. In the meantime it would seem that Longus’s most direct line of retreat back to Hadrumentum had been blocked by Caesar during some of his manoeuvres against Scipio. Longus became demoralised and decided to abandon the siege. He destroyed his stores, and then split up his army, giving part of it to Scipio. He then withdrew back to Hadrumentum, taking a route that took him inland through Juba’s kingdom.