Augustus
Augustus' reign laid the foundations of a regime that lasted, in one form or another, for nearly fifteen hundred years through the ultimate decline of the Western Roman Empire and until the Fall of Constantinople in 1453. Both his adoptive surname, Caesar, and his title "Augustus" became the permanent titles of the rulers of the Roman Empire for fourteen centuries after his death, in use both at Old Rome and at New Rome. In many languages, "Caesar" became the word for "Emperor", as in the German "Kaiser" and in the Bulgarian and subsequently Russian "Tsar" (sometimes Csar or Czar). The cult of "Divus Augustus" continued until the state religion of the Empire was changed to Christianity in 391 by Theodosius I. Consequently, there are many excellent statues and busts of the first emperor. He had composed an account of his achievements, the "Res Gestae Divi Augusti", to be inscribed in bronze in front of his mausoleum. Copies of the text were inscribed throughout the Empire upon his death. The inscriptions in Latin featured translations in Greek beside it, and were inscribed on many public edifices, such as the temple in Ankara dubbed the "Monumentum Ancyranum", called the "queen of inscriptions" by historian Theodor Mommsen.
The Twelve Caesars
Octavian (not yet renamed Augustus) finished the civil wars started by his great-uncle, Julius Caesar. One by one, Augustus defeated the legions of the other generals who wanted to succeed Julius Caesar as the master of the Roman world. Suetonius includes descriptions of these civil wars, including the final one against Mark Antony that ended with the Battle of Actium. Antony had been Octavian's last surviving rival, but committed suicide after his defeat at Actium. It was after this victory in 31 BC that Octavian became master of the Roman world and imperator (emperor). His declaration of the end of the Civil Wars that had started under Julius Caesar marked the historic beginning of the Roman Empire, and the Pax Romana. Octavian at this point was given the title ("the venerable") by the Roman Senate.