Answer: Rome becoming a republic.
The Roman Republic was an era in the history of classical Roman civilization. The then small state of Rome was previously governed by kings. However, in 509 BC, the people overthrew the government. They established a new system of government: a republic, which was intended to be more responsive to the needs and the will of citizens. The Republic lasted until 27 BC, when the Empire was established. The Republic was a period of great expansion, during which Rome came to dominate the entire Mediterranean.