Before Marius was back in Rome he was re-elected to the consulship (104 BC), though the law forbade re-election and required the candidate to be present in Rome.
But Marius was the soldier of the hour, and the hour demanded Rome's finest soldier of the day.
For during the Numidian war a tremendous menace had been gathering on the northern frontiers of Italy. The German tribes were making their first appearance on the stage of history.
The advance hordes of the Teutones and the Cimbri had rolled past the Alps and poured into Gaul, flooding down the valley of the Saône and the Rhône and also setting in motion the Helvetic (Swiss) Celts. They defeated the Roman consul Silanus in 109 BC and in 107 BC another consul, Cassius, was trapped by the Helvetii and lost his army and his life. In 105 BC the forces of the pro-consul Caepio and the consul Mallius were annihilated by the Cimbri at the Battle of Arausio (Orange), ancient sources estimating the the losses up to even 80'000 or 100'000 men.
Then for no apparent reason the tide relented for a moment.
Rome, desperate to use the time, turned to Marius, placing control and reorganization of her armies in his hands and making him consul year after year. And Marius did the unthinkable.
Marius reorganizes the Army
For a primarily agricultural society such as Rome to be a perpetual war machine is to attempt to combine two incompatibles.
What Tiberius Gracchus had tried to halt when he was tribune in 133 BC was a trend which had begun centuries earlier and which, by the very success with which Rome had conducted military operations, had become a vicious circle.
Ancient armies were armed by peasant farmers. A society constantly at war required a constant flow of conscripts. Smallholdings fell into disuse because there was no one to tend to them. As Roman conquests spread through the Mediterranean lands, even more men were required, and wealth and cheap corn poured back into Rome, much of it into the hands of entrepreneurs, who carved out vast areas for vegetables, vines, olives and sheep farming, all managed by slave labour. The dispossessed rural poor, became the urban poor - so becoming ineligible for military service as no longer being nominal property holders.
Not only was there therefore a shortage of recruits, but the soldiers had nothing to return to between campaigns or at the end of their service. A working solution to this problem was finally devised by Gaius Marius, once consul in 108 BC. He introduced the Roman army as it came to be known and feared all across the Europe and the Mediterranean.
Rather than conscripting from Roman landowners he recruited volunteers from the urban poor. Once the idea of a professional army of mercenaries was introduced, it never remained until the very end of the Roman Empire. Furthermore, Marius introduced the idea of granting soldiers allotments of farmland after they hand served their term.
Marius defeats the Northmen
Marius' revolution in the army came only just in time.
In 103 BC the Germans were again massing at the Saône, preparing to invading Italy by crossing the Alps in two different places. The Teutones crossed the mountains in the west, the Cimbri did so in the east.
In 102 BC Marius, consul for the fourth time, annihilated the Teutones at Aquae Sextiae beyond the Alps, while his colleague Catullus stood guard behind them.
Next in 101 BC the Cimbri poured through the eastern mountain passes into the plain of the river Po. They in turn were annihilated by Marius and Catulus at Campi Raudii near Vercellae.
Marius reaped the benefit of his joint victory with Catulus, by being elected to his sixth consulship.
