xviii Introduction (d. 363), who tried to revive paganism—Roman emperors from this time on were all Christian. Less than 75 years later, Theodosius the Great (d. 395) made Christianity the official religion of the empire. He was also the last emperor to rule the entire empire, for he divided the empire and put his two sons, Arcadius and Honorius, in charge of the eastern and western halves, respectively. Any examination of the Roman world entails a look at the fall of Rome, a topic of perennial interest. Historians from Gibbon down to today have often viewed the fall of Rome as an event, and there have been myriad theo- ries with specific dates and reasons for Rome’s demise. Some have argued that Rome fell in 476 when Romulus Augustulus, the last western emperor, died. Others argue that Emperor Justinian (d. 565)—who from the capital that Constantine founded, Constantinople, reconquered much of the former western empire in an amazing campaign—marks the fall of Rome. Most historians today, however, increasingly look at the fall of Rome not as an event but rather as a process, one in which Rome gradually transformed into three new polities. Various Germanic kingdoms in the west, all of whom looked to Rome for inspiration and many of whom considered themselves heirs to Rome, are one heir. The Byzantine Empire—whose people referred to themselves as the Romanoi (significantly, they called themselves “Romans” in Greek)—lasted until the 15th century and was another heir. The last heir to Rome were the Islamic peoples. Starting in the seventh cen- tury, Islamic forces swept from Arabia into the west and east, creating a new civilization that likewise looked back to Rome in many ways. These heirs, each of which kept alive something of Rome, preserved aspects of Roman culture at the same time that they created what became the three chief cul- tures of the Middle Ages.