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.
Coniuratio Italiae
The Oath of Italy ("Coniuratio Italiae") was an historical event taking place in 31 BC, by which Italy swore allegiance to Octavian Caesar in the Final war of the Roman Republic against Cleopatra and Mark Antony. Augustus himself retells the facts in the Res Gestae Divi Augusti: ""The whole of Italy voluntarily took oath of allegiance to me and demanded me as its leader in the war in which I was victorious at Actium."" Following the event, the Western provinces of Sicily, Sardinia, Spain and Gaul also sided with Augustus, and the same happened with the Eastern provinces and Egypt following the conflict. The Oath of Italy was foundational for the birth of the Roman Empire in a similar way the Oath of Brutus was declared to overthrow the Roman Kingdom, as both were used as an expression of the will of the people.