After the death of Julius Caesar, the Roman Empire was divided up and ruled by three of Caesar's former generals. These generals were Octavian, Marc Antony, and Marcus Lepidus. These three leaders formed what they called the Triumvirate. Each member of the triumvirate had absolute authority over matters that took place within their portion of the empire.
This triumvirate did not last long. Octavian forced Lepidus to retire from public life. Octavian then began planning a civil war against Marc Antony. Antony fell in love with and married a princess from Egypt by the name of Cleopatra. Octavian convinced the people that Marc Antony intended to take over Rome, and put Egyptian rulers in charge of affairs in the Roman Government. Octavian declared war against Antony in the name of the Roman Republic. By 31 B.C., Octavian defeated Marc Antony in Greece. In order to evade capture, Marc Antony and Cleopatra committed suicide.
Octavian was now the undisputed ruler of Rome. The republican government, which had been designed to rule a small city-state, had not been very effective at ruling the now massive Roman Empire. Rather than reform the republican form of government that they practiced, Octavian recommended to the Senate that one strong leader be put in place. The Senate elected Octavian as the consul and supreme leader of Rome for life.