Post-Caesarian civil war (44 BC), between the Senate army (led first by Cicero and then by Octavian) and the army of Antony, Lepidus, and their colleagues - Truce results in union of forces
Antony's civil war (32/30 BC), between the Western provinces (under the leadership of Octavian and Agrippa) and the East (under command of Marc Antony and Cleopatra) - Western victory
After 30 BC, the Republic was unified under leadership of Octavian Caesar. In 27 BC Octavian was granted the title of Augustus by the Senate, considered the end of the Republic and the birth of the Empire. The next Roman civil war would not be fought until after Nero's suicide in 68 AD; this period was known as the "Pax Augusti" (peace of Augustus), and was the beginning of the era known as the "Pax Romana" (Roman Peace).
In a war of propaganda, Octavian gradually convinced the western provinces, Italy, and most of the Roman upper class that Antony was sacrificing Roman interests, trying to become a Hellenistic king in Alexandria, and planning to rule the Roman world from there with Cleopatra.
By the end of the CivilWars and the beginning of the Augustan era, 2 million or 35% of the population in Italy were slaves.
To represent the continuing civilwars after the assassination of Caesar, Roman leaders that are killed are replaced 6 turns later with a successor: Octavian for Caesar, Sextus for Pompey, Antony for Crassus, and Brutus for Cicero.