those who criticized Augustus. Shotter suggests that Augustus's deification obliged Tiberius to suppress any open resentment that he might have harbored, coupled with Tiberius's "extremely conservative" attitude towards religion. Also, historian R. Shaw-Smith points to letters of Augustus to Tiberius which display affection towards Tiberius and high regard for his military merits. Shotter states that Tiberius focused his anger and criticism on Gaius Asinius Gallus (for marrying Vipsania after Augustus forced Tiberius to divorce her), as well as toward the two young Caesars, Gaius and Lucius—instead of Augustus, the real architect of his divorce and imperial demotion. Legacy Augustus created a regime which maintained peace and prosperity in the Roman west and the Greek east for two centuries. Its dominance also laid the foundations of a concept of universal empire in the Byzantine Empire and the Holy Roman Empires down to their dissolutions in 1453 and 1806, respectively. 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 Res Gestae is the only work to have survived from antiquity, though Augustus is also known to have composed poems entitled Sicily, Epiphanus, and Ajax, an autobiography of 13 books, a philosophical treatise, and a written rebuttal to Brutus's Eulogy of Cato. Historians are able to analyze excerpts of letters penned by Augustus, preserved in other works, to others for additional facts or clues about his personal life. Many consider Augustus to be Rome's greatest emperor; his policies certainly extended the empire's life span