He nearly doubled the size of the empire

Augustus began consolidating his rule, upgrading Rome's infrastructure, and beautifying the city after defeating his foes. He also wanted to expand the empire's borders, taking control of Egypt, northern Spain, the Alps, and much of the Balkans. In Germany, progress was made until three legions were killed out in an ambush in A.D. 9, forcing the Romans to retreat west of the Rhine River. According to a Roman historian, when Augustus learned of the defeat, he repeatedly slammed his head against the wall and roared at the general in charge to "give me back my legions." Augustus spent years in Spain, Gaul, Greece, and Asia as part of his expansion ambitions. Yet he was not much of a combatant himself, frequently falling ill on the night of battle and relying largely on his childhood buddy Marcus Vipsanius Agrippa for strategy.

Augustus virtually doubled the extent of the empire during his 40-year reign, gaining lands in Europe and Asia Minor and forging alliances that let him rule from Britain to India. He spent a lot of time outside of Rome, cementing control in the provinces and establishing a census and taxing system that connected the empire's farthest reaches. He reshaped Rome with both grand (a new forum) and practical gestures, expanding the Roman network of roads, founding the Praetorian Guard and the Roman mail service, and establishing the Praetorian Guard and the Roman postal service (police and fire departments).