Late Roman Army during the 5th century

[Flavivs Aetivs]

The west fell because of money - the west never had the money to sustain an adequate defense force without help from the Eastern Empire's rich provinces of Egypt and Anatolia.

Dunno where Majorian got the money for his force of c 460, or what might've been accomplished had it not been "preempted" by Geiseric. Anyway, the Western Roman Empire of 445 CE was roughly comparable in geographical extent to the Roman republic at the start of the second punic war. Resources may have been comparable. Strange that the republic could field enormous armies, and ultimately overcome a more formidable opponent than Geiseric. Times sure had changed.

The difference was that the Empire had the massive infrastructure of Gaul and Italy to maintain, along with a professional army rather than a Militia Army. In the republic you supplied your own equipment while in the Late Empire massive fabricae supplied rather standardized equipment for the whole army.

Not only that, but in the Republican Era most of the Farming was in italy - in the 3rd century agriculture began moving to Syria and Proconsularis/Numidia/Tripolitania. I read a lot about that in "Empires and barbarians" although I don't remember exactly why.