Gaius Marius was the Roman general known for his military reforms during the late Republic. In the 2nd century BCE, Marius introduced significant changes to the Roman army, allowing landless citizens to enlist and serve as soldiers, which transformed the military structure from a volunteer army of property-owning citizens into a professional force. This reform enabled greater social mobility and loyalty among soldiers, who were often dedicated to their generals rather than the state. Marius's changes contributed to the rise of powerful military leaders, leading to political upheaval in Rome. His legacy shaped military service and the dynamics of power during the Roman Republic.