Siege of Alesia — Caesar's Greatest Engineering Triumph
Caesar besieged Vercingetorix at Alesia in 52 BC by building two rings of fortifications, one facing in and one facing out. The Gallic revolt of that year had united most of the tribes for the first time under a young Arvernian noble who had adopted a strategy Caesar could not answer: refuse battle, burn the granaries and the towns, and starve the legions in a country they did not control. It had worked at Gergovia, where Caesar was beaten and lost 700 men. Vercingetorix then made his one mistake, attacking the Roman column with cavalry in open country, losing, and withdrawing into the hill fort of Alesia with some 80,000 men. Caesar had about 50,000 and no intention of assaulting it. His engineers built a line of circumvallation some seventeen kilometres round the hill — ditches, a rampart, towers every twenty-four metres, and belts of sharpened stakes and concealed pits the soldiers named after lilies and goads — and then, knowing that a Gallic relief army was coming, a second line of some twenty-one kilometres facing outward. The relief arrived in late September, variously reported at 240,000 and certainly enormous, and attacked the outer line while the besieged attacked the inner one on the same days. The crisis came at a weak point on the north-west, where Labienus held with the last reserves and Caesar arrived in a red cloak with the German cavalry behind the attackers. Vercingetorix surrendered the next day and was displayed in a triumph six years later and strangled. The site was identified in the 1860s by an excavation Napoleon III paid for, which found the ditches and the stakes almost exactly where the Commentaries put them. Vercingetorix became a French national symbol in the same decade, which is a curious afterlife for a man whose defeat made Gaul Roman.
- Year: 52 BCE
- Category: Military
