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. Augustus dramatically enlarged the Empire, annexing Egypt, Dalmatia, Pannonia, Noricum, and Raetia, expanding possessions in Africa, and completing the conquest of Hispania, but suffered a major setback in Germania. Beyond the frontiers, he secured the Empire with a buffer region of client states and made peace with the Parthian Empire through diplomacy. He reformed the Roman system of taxation, developed networks of roads with an official courier system, established a standing army, established the Praetorian Guard, created official police and fire-fighting services for Rome, and rebuilt much of the city during his reign. Augustus died in AD 14 at the age of 75, probably from natural causes. However, there were unconfirmed rumors that his wife Livia poisoned him. He was succeeded as emperor by his adopted son (also stepson and former son-in-law) Tiberius.
Gaius Julius Caesar: After he was adopted by Julius Caesar, he adopted Caesar's name in accordance with Roman naming conventions. While he dropped all references to the Octavius family, people colloquially added the epithet Octavianus to his legal name, either to differentiate him from his adoptive father or to highlight his more modest origins. Modern historians refer to him using the anglicized form "Octavian" (n/) between 44 BC and 27 BC.
Gaius Julius Caesar Divi Filius: Two years after his adoption, he founded the Temple of Caesar additionally adding the title Divi Filius ("Son of the Divine") to his name in attempt to strengthen his political ties to Caesar's former soldiers, following the deification of Caesar.
Imperator Caesar Divi Filius: From 38 BC, Octavian opted to use Imperator, the title by which troops hailed their leader after military success. His name is roughly translated as "Commander Caesar, Son of the Divine".
Imperator Caesar Divi Filius Augustus: Following his 31 BC defeat of Mark Antony and Cleopatra, partly on his own insistence, the Roman Senate granted him the additional name, "Augustus"., which he added to his previous names thereafter. Historians use this name to refer to him from 27 BC until his death in AD 14.