ABSTRACT
The late Roman army was ultimately a product of the reforms of Diocletian and the more far-reaching measures taken by Constantine, but a discussion of its origins must begin in the late second century in order to illustrate the background to the reforms of these two emperors. There are certain landmarks in the origins of the late Roman army, conventionally placed by modern scholars in the reigns of Marcus Aurelius, Severus and Gallienus. Any evaluation of the development of this army must take these landmarks into account, but with this proviso: that it is important to realize that the successive remodelling of the army that occurred between the reigns of Marcus Aurelius and Constantine was not undertaken as part of a steady progression by logical stages towards an established goal. The benefit of hindsight enables scholars to discern, in the changes in military organization made by Marcus, Severus, Gallienus and Diocletian, the embryonic forms of the later army, with the result that it seems that there are definite links in the chain of development connecting the armies which Marcus Aurelius assembled on the Danube, with the later field armies of Constantine. This is not, strictly speaking, the case, and has been the subject of debate for nearly a century.
