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.
Constitutional reforms of Augustus
The Constitutional reforms of Augustus were a series of laws that were enacted by the Roman Emperor Augustus between 30 BC and 2 BC, which transformed the Constitution of the Roman Republic into the Constitution of the Roman Empire. The era that began when Augustus (then named Imp. Caesar Divi Filius, but often called Octavian by historians) defeated Mark Antony and Cleopatra in the final war of the Roman Republic in 30 BC, and ended when the Roman Senate granted Augustus the title ""Pater Patriae"" in 2 BC.