By the first century BCE, Rome had gained control of the entire Mediterranean, but those conquests had been accompanied by a century of civil war that witnessed the assassination of politicians on all sides of the political spectrum. At one point, the adherents of one populist politician marched on Rome's temple of Castor and Pollux, which was closely associated with the Senate, and tore up the temple steps. This period of nearly continuous warfare would not end until 31 BCE, when Julius Caesar’s nephew Octavian vanquished the combined forces of Mark Antony and the Egyptian queen Cleopatra at the battle...