Gaius Octavius was eighteen years old when Julius Caesar was assassinated in 44 BC, and nobody thought he mattered. He was Caesar’s great-nephew, slight and sickly, without military reputation or political standing. He had one asset: Caesar’s will named him adopted son and primary heir. He used that asset with a patience and calculation that none of his older, more experienced rivals understood until it was too late.

The name by which history knows him — Augustus, the revered one — was a title conferred by the Senate in 27 BC, seventeen years after Caesar’s death and four years after he had defeated Mark Antony and Cleopatra at the Battle of Actium, eliminating the last serious rival to his control of the Roman world. Between the teenager nobody feared and the man the Senate was now calling Augustus lay fourteen years of civil war, shifting alliances, calculated betrayals, and the systematic elimination of everyone who stood between Octavian and sole power. He was very good at it.