In the wake of the assassination of the Gracchi, which demonstrated that political reform through traditional means could be stymied or prevented through violence, Roman citizens and soldiers increasingly rallied around rich and powerful men, who used their great wealth and power to provide for their supporters. The close allegiance of soldiers to their military commanders degraded a shared sense of purpose among the Romans and allowed individuals to amass extraordinary power and influence. Moreover, the rivalries between these strongmen frequently led to conflict and violence between them and their partisans. It is easy for the history of the Late Republic to be a study simply of these “great men.” All of them achieved some good things for Rome; all of them also either brought great destruction to Rome or paved the way to autocracy. At times, they exploited aristocratic sentiments, at others they played upon the emotions of the common people. They all profited personally whether their constituents did or not.

Gaius Marius was the first of Rome's strongmen of the Late Republic; others would follow—Sulla, Pompey, Caesar, and Augustus, all of whom will be discussed in subsequent chapters. Marius came from relatively humble origins. He started out as a new man (novus homo), a technical term indicating a politician who was the first of his family to attain the senate, or even more exclusively the first to reach the consulship. Although Marius did not have an aristocratic legacy, he did have ambition and talent, particularly military talent. Politically, he tended to favor popular measures, such as his bill in 119 BCE as tribune of the plebs to prevent voter intimidation in the assemblies, an example of a benefit he provided the political system.

Marius rose to the forefront of Roman politics during the war with Jugurtha in North Africa, which broke out in 112 BCE. Jugurtha showed himself a difficult opponent to defeat. Several rounds of generals failed to bring the war to completion. Marius had been serving in the war under the commander Quintus Metellus when he returned home to seek the consulship for 107 BCE, which he won in large part because of popular support.