ABSTRACT
In Roman history, the fourth century c.e. is often reckoned from the acclamation of Diocletian as emperor in 284 to the death of Theodosius in 395. The real turning point between the third and the fourth centuries, however, is the death of Carinus in 285. The gigantic mobilization required to meet Rome’s difficulties over the third century had furthered the trend toward an absolute military monarchy that can already be seen with Commodus and Septimius Severus. Under Diocletian, the Principate gave way completely to the Dominate. Diocletian and his co-emperors, then Constantine and Constantine’s heirs, spent prodigiously on building in Rome, Constantinople, and other important cities where emperors frequently resided, such as Trier, Milan, Sirmium, Nicomedia, and Antioch. During the third century, Rome’s system of frontier defense had essentially collapsed. In the latter part of the century, Gallienus and his capable Illyrian successors surrendered control of the Empire’s eastern and western periphery and concentrated on holding its central core.
