In 53 BC many tribes of Gaul united against the Romans, under the leadership of Vercingetorix. After his defeat in a rash cavalry engagement in 52 BC, Vercingetorix and his forces withdrew into the impregnable hilltop 'oppidum' of Alesia.
Caesar laid siege to the stronghold, surrounding the plateau with a ring of eight cavalry and infantry camps.
Vercingetorix tried to break out, and by night succeeded in sending away his cavalry to seek reinforcements.
The Romans dug ditches, pits with sharpened stakes and other traps to hinder any further breakouts, and constructed a defensive wall with towers at intervals.
Finally they erected a 14 mile (23 km) outer rampart and a number of redoubts which they garrisoned.
A vast Gaulish army, outnumbering Caesar's soldiers five to one, arrived to relieve the besieged Gauls and set up camp behind the Roman lines.
They attacked, supported by Vercingetorix's troops. The engagement was close-run but eventually the Romans won the day.
Vercingetorix attempted to fill in the ditch. Night attacks were made on the Roman lines but these also failed.
The Gauls moved round to a new attack position where Roman cavalry attacked them in rear and routed them.
The relieving force of Gauls fled and Vercingetorix surrendered.
