When did the Roman Army lose it\'s...

[Justin I]

Several good responses here, I would only add that by the 4th and 5th centuries AD, the Romans no longer had as much of a technological advantage over their enemies. The Germanic tribes were better equipped by that point than the ones that faced Marius centuries earlier.

We could say, then, that the late Roman army did not fail the state, but rather that the state failed the army...

I agree. But this creates another interesting question: why did the state fail? I personally think that the conquest of Africa by the Vandals, which cut off the food supply of Italy, was the most important cause. Within six years, the tax department had been abolished.

It's interesting to wonder how things might have turned out if Majorian or Basiliscus had managed to take Africa back.