Caesar knew the senate was going to have him killed for his behaviour in Gaul so he took his leigon and went against the constitution by entering Rome with weapons.
The opposition party fled the city into Greece. The opposition party had recruited Romes other top experienced General Pompey and had him lead the loyalist force.
Caesar crushed them all the way across the eastern Republican Jurisdiction, essentially performing a clean sweep through all of the the friendly and allied provences in the entire jurisdiction that left them formed into one nation.
What Caesar was doing was suspending fluid lawmaking to achieve a settling a uniforming of culture, a dictatorship of the proletariat.