Final answer:
Gaius Marius, a Roman leader of the populares, initiated military reforms that eliminated property requirements for army enrollment, leading to the formation of professional armies loyal to generals like himself.
Step-by-step explanation:
Gaius Marius was a Roman general and politician who became the leader of the populares. He was elected consul an unprecedented seven times, starting in 107 BCE. Significant for his military reforms, Marius allowed the poor, the proletariats, to enlist in the army, thus forming professional client armies that were highly loyal to their generals rather than the Roman state. This was a drastic change from the traditional system where soldiers were mostly land-owning citizens. His reforms had profound long-term effects on Rome, contributing to the shift away from the Republican system and setting the stage for the dominance of military strongmen.
The entrance requirements for the army were dropped, allowing many poor citizens to join and serve under military commanders who promised war gains and land. Such armies eventually helped Marius to take Rome by force in 87 BCE, demonstrating loyalty to him rather than to the traditional Roman political and legal systems. This personal loyalty of the armies became a model for future generals as well, influencing his contemporaries and successors like Sulla, who similarly used their military might to gain political power, further destabilizing the Roman Republic.
Ultimately, Marius's reforms created a new dynamic in Roman politics and the military, where power leaned increasingly towards individual generals and away from the Senate. His clientele army system also meant land distribution became tied to service in these personal armies, complicating the traditional Roman virtue of serving the state over personal gain.