Historians from the time of the Roman Empire up to modern times have held strong opinions on the life and character of Gaius Marius. Best known for being the uncle of the famed Julius Caesar, he has also been regarded as barbaric, displaying unbridled ambition and by some accounts as having an evil influence on the Roman Empire. At the same time however, he also achieved high ranks in both politics and the military in ancient Rome, despite being an outsider and hailing from a family with no political ties. He is also credited with revolutionizing Rome's army, with the changes he instituted being widely regarded as the greatest contribution to the organisation of Roman legions.

Born to an equestrian family in the Italian countryside, his family is known to have been locally influential, but had no ties to anyone in high ranks in Rome - neither in the military or in the political arena. Despite this start in life, Marius was determined from the beginning to break into the high ranks of the republic. From his beginnings in the Roman army, he quickly moved up through the ranks; due most likely to having caught the attention of those in power with his drive and ruthlessness. Using his successes in the military he sought power in politics which has been widely regarded as having been attained unlawfully.

Through a special election which was deemed underhanded by the Roman senate, Marius attained commander-in-chief of Rome's African legions, and from this position he made the changes to the army for which he is known. In the past, Rome had only accepted soldiers who had land and wealth, who were able to purchase their own armour and supplies. It was thought that men of means would make good soldiers as they had something to lose in battle. These requirements meant that many men were ineligible to serve giving fewer options to the poor masses that filled the streets of Rome and other cities in the Empire.

These were not peaceful times; the had been at war for the entire second century and Marius saw the potential in the Roman mob. Going for pure manpower he enlisted these men, in effect giving them full time employment, purpose in their lives and the promise of land upon retirement. These changes produced a different type of soldier; a soldier loyal to his general and driven by his potential status and wealth should he be successful. Their military became their lives and their lifelong careers of choice.

Marius also made changes in the way his soldiers fought and moved, and to the weapons they used. The throwing spears soldiers used were altered so that the tip of the spear broke on impact making it useless to enemies once loosed. He also had the soldiers carry all of their own provisions on their backs, making the need for long baggage trains unnecessary.

Marius also began promoting officers who showed potential within the ranks rather than relying on political connections as had been done in the past, making for more experienced and superior officers, further strengthening the army.

Although Marius proved successful in both his political and military careers, his achievements were attained ruthlessly and in some cases unlawfully. He experienced failures as well on both fronts but like so many great historical figures he is most known for his achievements and positive contributions rather than his failures.