"The die is cast" - Julius Caesar
The last century BCE marked an age of civil war between the people of the Republic. Reforms and changes to the system pushed the Republic to the brink, and eventually it emerged as an Empire. The "last man standing" would be known as Augustus, but many came before him.
A clear break between the elite had formed. There were those who valued their lineage above all, calling themselves the optimates, "the best qualified", and those the optimates dismissed as populares "popularity seekers". The populares sought power through the people.
This period saw the rise of the enemies and rivals, Marius and Sulla. Marius introduced several military reforms to adapt to the changing time but these reforms would lead to civil war. Sulla would grasp the opportunities these reforms. Sulla would march on Rome with retired soldiers who felt more loyalty to Sulla than the Senate.
With the force of his army Sulla seized power as Dictator, placed down his own reforms in an attempt to stop the splintering of the republic. However, his actions simply showed to later ambitious general how they too could seize power with their own armies.
Generals such as Julius Caesar and Pompey would take power over the Republic, forming the first triumvirate.