Damned Muslims

[Cerrone]

So to put it simply; the Romans eventually realised that there was no point waging war on barbarians when it was so easy to delude them into passivity under christianity.

Nah. Gives xtians too much credit for things. The church found a way to survive without their Roman patrons and by the end one had become indistinguishable from the other. Mainly they did this by conning the barbarians.

Constantine's biggest error was political. Noting that the army was the single biggest de-stabilizing force ( and he would have known since he used his army to rebel against the sitting emperor ) he downgraded the legions into a force called the limitanei, basically border guards, without the discipline and training of the legions. In order to forestall revolts by disaffected generals, as he had been, he created a mobile reserve army (the comitatenses) which was under his personal command. The system quickly broke down as even with Roman roads the army could not meet every threat in time and the limitanei were ill-equipped and ill-trained for prolonged resistance. It became necessary to make detachments and this re-created the problem of jealous generals under a new name.

The major error, which Constantine tried to undo but eventually failed, was the division of the empire into East and West under Diocletian. In short, the West did not have the economic resources of the East and with them separated there was no more of the East subsidizing the west.
"The sinew of war is infinite money," to quote M. Tullius Cicero.

I know you've done your research on this too, but were you aware that the first bishops in the roman church were the same wealthy patricians who were high priests in the old roman religion? The says to me that the church then had nothing to do with any kind of spiritual revolution and was more like a rebranding of product.

The East/West division itself had pretty much existed since the triumverate with Octavian and Mark Antony since the provinces were far too large and distant for Rome to effectively govern as the capitol of such vast and distant outposts. But all provinces were self sufficient and capable of sustaining at least themselves. The wealth of the provinces in Syria and Byzantium though meant that Rome wouldn't ever let them seperate away from it, thats even more reason for Rome to have taken up the spiritual/propaganda status while Byzantium and the levant territories were the military frontier.