He selected the plains on the banks of the Rhone in Southern Gaul as best adapted for his purpose.

Here he drilled his troops, accustoming them to the greatest possible exertions.

Many perished under the strain, but the survivors became hardened soldiers.
Corps of engineers were attached to each legion, and the soldiers were taught the use of tools, as well as of arms.

At length, in his fourth consulship (102), he felt prepared to meet the enemy.
The barbarians, on their return from Spain, separated their forces, the Cimbri marching around the northern foot of the Alps towards Noricum, with the intention of invading Italy from that quarter, while the Teutones remained in Gaul.
As the latter advanced, Marius took up his position in a fortified camp near AQUAE SEXTIAE (Aix).

He allowed the enemy to march past him, and then followed cautiously, waiting for a favorable opportunity to fall upon them.