Gaius Marius was himself a rising Equestrian client of the Metelli. After ten years of service, Marius stood for election as a military tribune, a legionary staff officer elected by the soldiers themselves. He most likely spent his year as military tribune in the Balearic Islands helping one of the eldest Metelli cousins achieve the generation’s first triumph. He parlayed this service into a successful run for his first true magistracy, winning a quaestorship in 122. In office, Marius probably served in the legions that were by then advancing into southern Gaul. There he would see for the first time the hills and streams where twenty years later he would win one of the most spectacular victories in Roman history.10
WHEN ROME EXPANDED beyond the borders of Italy it moved in three directions: west to Spain, south to Africa, and east to the Aegean. But their northern border remained unchanged, partly because the Alps loomed as an enormous natural boundary. But after the great conquests of the mid-second century, Rome needed to maintain supply and communication lines with its far-flung territories in Spain and Macedonia. As a result, the legions crossed the Alps and became embroiled in a series of conflicts with the tribal powers beyond the new frontiers.11
Until the 120s, however, the swath of coastline between the Alps and Pyrenees was not under Roman jurisdiction. They instead left the protection of the region to the city of Massilia. A Greco-Phoenician colony founded in the 600s, Massilia had been a friend and trading partner of Rome going back to the early days of the Republic. In 125, Massilia was attacked by the Salluvii—a Gallic tribe that dominated the plains between the Alps and the Rhône river—and they requested aid from Rome. Happy to help a friend (and even happier to get the consul Flaccus out of town before he pushed through his bill for Italian citizenship), the Senate dispatched legions north. After several years of inconclusive fighting the Romans finally occupied a settlement about twenty miles inland from Massilia and organized it as a permanent military colony called Aquae Sextiae (modern Aix-en-Provence). After its founding in 122, Aquae Sextiae became the principal base of Roman operations in Gaul.12
Repulsed by the Romans, the king of the Salluvii took the remnants of his people and sought refuge with the Allobroges, another powerful tribe that controlled territory in the upper reaches of the Rhône. With the Allobroges lurking, the Senate dispatched the consul for 122 to guard the frontier. Late in the year, the legions won a huge battle against the Allobroges near modern-day Avignon, and followed that up a few months later with an even bigger victory—a victory that quaestor Gaius Marius likely participated in. The climax of these early Gallic wars came in the late summer of 121. The Romans met a coalition of Gauls eighty miles north of Aquae Sextiae on the banks of the Isère River. We have no details of the battle but with total Gallic losses estimated at 120,000, it must have been a huge affair. Only a lack of specifics in the record keeps the Battle of the Isère River from being one of the most famous battles in Roman history. The victory established Roman political and military hegemony over southern Gaul.13
With the Romans ascendant in Gaul, a faction of senators and Equestrian merchants pushed to found a permanent civilian colony in the region to facilitate supply lines in case of future emergencies. The Senate twisted itself into contortions resisting the proposal, but just as they were achieving terminal paralysis, the dazzling young orator Lucius Crassus delivered another impressive performance in the Assembly. He strongly advocated for the founding of the colony and carried the Assembly—and most of his senatorial colleagues—along with him. When the new city of Narbo (modern Narbonne) was finally founded in 118, the whole region of southern Gaul became known as Gallia Narbonensis. With permanent settlements in the area, the Romans then constructed the famous Via Domitia, the permanent road linking Italy to Spain that is still visible along the southern coast of France.14
AFTER PARTICIPATING IN wars in Spain in the 130s and Gaul in the 120s, Gaius Marius transitioned from military to civilian life and stood for the tribunate of 119. He secured election thanks to the patronage of the Metelli. But rather than use his year as tribune to win new friends and allies, Marius spent his time alienating nearly everyone.15
