The Battle of Actium was also an important turning point in the history of the relationship between Egypt and Rome. When Octavian (later known as the Emperor Augustus) met the combined Roman forces of Mark Antony and the Egyptian forces of Cleopatra, Roman forces faced Roman (and allied) forces, pretty evenly matched. The fighting continued throughout the day of September 2, 31 B.C., until, inexplicably, Cleopatra took her troops and left the naval battle. Mark Antony, leaving his troops behind, followed her. The result was that Octavian, helped by his right-hand man, Marcus Vipsanius Agrippa, won the battle.
Antony, Octavian and Marcus Aemilius Lepidus had formed what we call the second triumvirate, but by the Battle of Actium, Lepidus had already been exiled. With the defeat and suicide of Mark Antony, all that remained of the triumvirate was Octavian as the leader of Rome. He would soon become Augustus (originally an honor, a title, rather than a name), the princeps (a term from which we get the word "prince"), and the first Roman emperor (a term that comes from the Latin "imperator" a term with which troops hailed a victorious general). [See Pennell's History of Rome.]