Caesar Augustus[1][2] (23 September 63 BC – 19 August AD 14), also known as Octavian, was the first Roman emperor, reigning from 27 BC until his death in AD 14.[nb 1] His status as the founder of the Roman Principate (the first phase of the Roman Empire) has consolidated a legacy as one of the most effective leaders in human history.[3] The reign of Augustus initiated an era of relative peace known as the Pax Romana. The Roman world was largely free from large-scale conflict for more than two centuries, despite continuous wars of imperial expansion on the Empire’s frontiers and the year-long civil war known as the “Year of the Four Emperors” over the imperial succession.