How did the government of rome develop into an empire

First was the Roman Republic, then came the Roman Empire. In the 4th century BCE, the Roman Republic turned to imperialism. After losing a significant battle with the Gauls, a Celtic people, the Romans concluded that in order to sustain safety, they would have to expand their territory so the frontiers would be a good distance from the capital, Rome. They successfully fought a series of wars with other Italian city-states as well as the Carthaginians, achieving their goal. Warfare gave excessive power to the military leaders, weakening the influence of the Senate and thus the democracy became undermined. That is how it was transformed to a vast empire.