Changes in the political atmosphere caused the Roman Republic to become engulfed in chaos and civil war. A dictator was elected in 82 BC, serving until 80 BC. After his formal resignation in 79 BC, Rome returned to a state of unrest. While Rome would continue to be officially governed as a republic for another 50 years, a gradual transition to Imperialism and permanent dictatorship began with the rise to power of Julius Caesar in 60 BC.

By 51 BC, Caesar had successfully conquered Celtic Gaul, expanding Rome's borders outside the Mediterranean region for the first time. While Rome was still nominally governed by the Senate, its power was weakening. In 44 BC, Caesar was assassinated. He was subsequently succeeded by his heir, Octavian, along with Mark Antony. Antony died in 31 BC during the Roman conquest of Egypt, leaving Octavian as Rome's unchallenged ruler. Octavian then became the first Roman emperor, assuming the title of Caesar Augustus.