What cause the Roman Republic to change to the Roman Empire?

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The Roman Republic was founded when after the last Etruscan king was overthrown in 509 B. C. Rome's next government served as a representative democracy in the form of a republic. During the time of the Roman Republic the top leaders of the Roman government were the consuls. There were two consuls at a time and they only served for one year. This kept any one man from becoming too powerful.

Two thousand years ago, the world was ruled by Rome, but Rome could not rule itself. It took two men to wrestle Rome back from chaos and turn a republic into an empire. In the first century BC, Rome was a republic. Power lay in the hands of the Senate, elected by Roman citizens. But the senators were fighting for power between themselves. Order had given way to anarchy and only might was right.