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.
Parthian Empire
Following the defeat of Antony and Cleopatra of Ptolemaic Egypt at the Battle of Actium in 31 BC, Octavian consolidated his political power and in 27 BC was named Augustus by the Roman Senate, becoming the first Roman emperor. Around this time, Tiridates II of Parthia briefly overthrew Phraates IV, who was able to quickly reestablish his rule with the aid of Scythian nomads. Tiridates fled to the Romans, taking one of Phraates' sons with him. In negotiations conducted in 20 BC, Phraates arranged for the release of his kidnapped son. In return, the Romans received the lost legionary standards taken at Carrhae in 53 BC, as well as any surviving prisoners of war. The Parthians viewed this exchange as a small price to pay to regain the prince. Augustus hailed the return of the standards as a political victory over Parthia; this propaganda was celebrated in the minting of new coins, the building of a new temple to house the standards, and even in fine art such as the breastplate scene on his statue Augustus of Prima Porta.
Along with the prince, Augustus also gave Phraates IV an Italian slave-girl, who later became Queen Musa of Parthia. To ensure that her child Phraataces would inherit the throne without incident, Musa convinced Phraates IV to give his other sons to Augustus as hostages. Again, Augustus used this as propaganda depicting the submission of Parthia to Rome, listing it as a great accomplishment in his "Res Gestae Divi Augusti". When Phraataces took the throne as Phraates V ("r". c. 2 BC – 4 AD), Musa married her own son and ruled alongside him. The Parthian nobility, disapproving of both the incestuous relationship and the notion of a king with non-Arsacid blood, forced the pair into exile in Roman territory. Phraates' successor Orodes III of Parthia lasted just two years on the throne, and was followed by Vonones I, who had adopted many Roman mannerisms during time in Rome. The Parthian nobility, angered by Vonones' sympathies for the Romans, backed a rival claimant, Artabanus III of Parthia ("r". c. 10–38 AD), who eventually defeated Vonones and drove him into exile in Roman Syria.