Marius exposed the rift of the late Republic. It wasn't his intention, and this practice of exposing system failures wasn't his idea either. He was responding to the pressures of his time, but he didn't understand the consequences.
Marius was of ancient Latin descent, and his people had recently become official Roman citizens (with the right to vote). This is important because it explains some of his compassion. He is from the Alpino region:
They have been part of Rome since the Second Samnitrian War (326-304 BC). The situation in the area indicates that they are Volsi and not Samni, as they are citizens but cannot vote. In other words, the people of Marius fought for Rome for more than a hundred years until they gained the right to participate in politics in 188 BC.
His family may have been part of the local nobility, but this made no sense in Rome until 188 BC. So, for the Romans, Marius was a "newcomer," even though he came from a family of status and wealth.
That kind of thing is a pain point. Many people like Alpino, who were loyal to Rome during the Second Punic War, gained full power after that war. Many others don't.
Now that we understand the context, let's look at legions. In Marius's youth, the Legion continually lost manpower. Not a war, but a disqualification of qualified recruits due to property damage. The Legion is made up of such people:
In order, they are hastati, velites, triarii, and principes. There is no need to explain their roles, but know that everyone is the landowner, who is acquired according to age and wealth. Citizens without land have no services.
Until the proto-Germanic peoples rushed out of Jutland and smashed the ball of destruction at the armies of Gaul and Rome:
In total, more than 100,000 Romans were killed. Essentially, Rome had now shed its old legions, but still needed an army.
We're actually not sure how many people died under the Roman flag. Why? Usually, more than half of any Roman army deployed during that period consisted of "allies" that looked like this:
They looked and functioned like legionnaires, but they appeared in queue-sized units attached to deployed armies. These allies were not citizens and received a smaller share of the plunder from the war; they often said indignantly. Sometimes ancient sources count them, sometimes they don't.
They received benefits, but these were decided by their Roman masters, who had no say in when, where, and when they were deployed.
Let me return to the main topic, Rome did not have legions to replenish its army, and not only was the war not over, the original Germans could turn to Italy (they were in Spain) at any time. Marius now needed soldiers, so he pushed for the law of renouncing property claims and opened the legions to landless citizens; he said for the time being. Since these people went bankrupt, the government paid for their equipment. The government will be equipped with all these legionnaires as a principle:
Training was standardized, legionnaires carried most of his equipment, increased manpower, changed the design of javelins, and so on. How did Marius increase his manpower while maintaining the same number of Legionnaires? In fact, 40% of the older legions are not part of the rotation:
Usually, velites retreat to the rear before they are fully engaged, and Triarii are veterans who will serve as a last resort if everything falls apart. Marius swept them all into the front, and now everyone was the principle.
At the same time, the Romans slanted toward their allies. Those who looked and fought like Romans but did not have Roman rights.
The Romans hastily rebuilt it. The Cymbrians and Teutonics were still there, ready to invade Italy. For reasons we don't know, they hunted down the proto-Basques in northern Spain. We don't know anything about that war. We know they were repulsed and re-entered Gaul in the confusion. This time, the Romans were convinced that Italy would be their target. Before Italy was invaded, Marius pursued them with his rebuilt army:
Marius won the war with his new army and allied service, with very low losses. It is appropriate to reward those who saved Italy. What do these people want?
Large numbers of landless people want land, and allies want citizenship and land. The Roman Senate would not fulfill their wishes. As a result, soldiers, citizens, and allies all stopped paying attention to the Senate and turned to their generals. Marius delivered.
That decade of fear and the changes it caused had a series of unintended consequences:
For the unfettered soldier, being a soldier became a permanent job for the Romans. The camp became home. Roman soldiers were already excellent and became better as full-time professionals. The Roman army was simplified, standardized, logistically improved, etc.
These full-time professionals are different. For the most part, they have no sense of loyalty to the country. Roma never did anything for them and actively participated in evic taking them away from their land, leading to his poverty. However, he was recruited, paid, and rewarded by his generals, not by Roman politicians.
Soldiers told the generals they wanted land in exchange for services, and the generals did their best to provide them.
The allies always knew how important they were to Rome's power. They had an advocate in Marius. Marius obtained many full citizenships. He claimed that in battle, he could not distinguish (very correctly).
The instability associated with the one-year dual consular system is beginning to be intolerable. The system is crashing. There should be a 10-year gap between people. The Senate, in a panic, appointed Marius consul for four consecutive years (6 in all). It was clear that the Roman administrative system was not sufficient to administer the empire.
The old aristocratic/commoner divide was permanently destroyed. A new optimized and popular structure takes its place. Many of the popular people came from ancient aristocratic families. Many of the optimizations come from civilian stocks. It doesn't even have to do with wealth.
During this time, one of Marius's disciples, Sulla, rose up against Marius.
By and large, Marius was pro-ally, pro-civilian, and reform-oriented. His opposition Sula and friends are very close to the Senate, pro-rich, anti-allies, anti-civilians, etc.
All of this ended in violence on the streets of Rome. With the support of soldiers and veterans, mob rule took control of politics. Politicians of one or the other party are convicted, murdered and property confiscated for political leaning.
I need to emphasize that there are no clear boundaries in this segment. This split took place in families and Roman clans
Marius, a wealthy commoner, was opposed by Sulla, a poor noble clan.
Moreover, we cannot think of it as a traditionalist and a reformer. For example, Sulla was freed from the powers of a consul, the constitutional office of the early republic.
With marius and Sulla following, Rome's political system collapsed. Its constitution broke down and institutions began to fail. It wasn't Marius's fault, it had begun to decay decades before he took office. However, Marius embarked on 50 years of political and military turmoil that eventually destroyed the Republic.