8. After Removing His Enemies, Octavius Went After His Former Partner
After defeating their enemies, Octavius and Mark Antony swore friendship, and sealed their agreement to share power with Antony wedding Octavius’ sister. They then divided the Roman world, with Antony ruling the east, while Octavius stayed in Rome and ruled the west. However, the duo fell out when Antony fell in love with Cleopatra in Egypt, and married her, abandoning Octavius’ sister.
The future emperor used that family insult as a pretext to attack Antony. He defeated his former partner decisively in 31 BC, and became Rome’s sole ruler and de facto dictator. He then seized Egypt and the eastern provinces, which finally brought the entire Roman world under his control.