Marius and Sulla work together to lead an army in Northern Africa and ultimately defeat Jugurtha. Following that success, and after many political twists and turns, the two travel to Gaul-across-the-Alps to battle and turn back the German and Celtic tribes who are moving into Italy. Along the way Marius changes the course of history greatly when he becomes Consul in abstensia (not physically present in Rome during the vote) 3 times and is ultimately Consul 7 times. Republican tradition and laws forbade someone from being Consul two times in a row, but Marius was Consul more than 5 times in a row.
Besides the "barbarian enemies" that the two men battle, they also battle on the political stage. There is a conservative group of senators (who call themselves the Boni or Good Men) who like things the way they always have been - rich, aristocratic, Romans of Rome running Rome without much input from the lower classes. Marius and the other New Men (Roman citizens that were not of the old families and/or had ancestors who were slaves or farmers outside of Rome) realize that the masses are a strong and persuasive source of political power. They harness the power of the "Head Count" (men with no-property and who are poor and therefore "don't count" to the Boni) in both military action and political support.
The First Man in Rome is quite a large book, but it gives personality to the generals and political people in this historic period of the Roman Republic. I became invested in the lives of the people during what would normally be long battle scenes while the generals are away from Rome fighting the enemy. It is a great novel and would be a good introduction to the lives and times of the pre-Civil War Republican Rome.
