When Justinian first assumed the title of Roman Emperor in 527 CE, his inherited empire--now based in Constantinople-- had lost almost all of its connection with the Eternal City itself, and was threatened from within by profound theological splits, and from without by the various barbarian kingdoms that surrounded it. By taking military action against the barbarian Ostrogoths, Visigoths, and Vandals, and signing an eternal peace with Persia, Justinian...