Germanic Urbanisation & Infrastructure Post Augustus

[Robert Vermaat]

However, I do think we can see the various 'barbarian' groups being considerably more effective in the third century than they were during even the Marcomannic war, when they only got as far as Aquileia. 

Would that not have been caused by the military crisis of that period? I mean, how often did Germanic invaders penetrate the Western Empire that far during most of the fourth century? Their growing success after Adrianople and during the fifth century would (again) be mostly due to Roman military misery and of course mistakes on the battlefield. 

As I say, though, most actual battles were Roman victories. And, just as with the fifth century, we can no longer claim that barbarian incursions caused the crisis; rather they took advantage of it, exacerbated it, and prolonged it.

Why can we not? The cause of the problem was the concentration of Roman forces on the borders, but that had been the case as well during the first and second centuries, when it was not a problem. If this became a problem only due to the forming of Germanic federate tribes, the question remains why this had not happened earlier - germanic tribes could and did work together earlier yet did not seem to present that much of a problem. In my opinion is was far more due to the weakened Roman border defences because of the crisis (also accompanied by a relative paralysis of the military structure as a result of the crisis). 

This was adjusted by the development of the later 'defence-in'depth' system of the limitanei / comitatenses which also gave the military command to the comites and duces responcible for the endagered sectors, and even that was not enough to prevent deep incursions of the enemy, especially when the military was involved in a form of political crisis. Which would prove my point.

So there's no need, on the face of it, to assume that 'barbarian' armies of the 3rd-4th centuries were necessarily better armed or equipped, or better organised, or that their societies were necessarily more advanced than they had been in the 1st-2nd. They probably were in some respects, but in ways that has left little hard evidence. Only by the 5th century do we see a definite change, and by then the 'barbarians' are operating inside the empire anyway.

Maybe better organised in the sense of mutual cooperation? 

On the vexed question of ethnogenesis and 'supertribes': the constant movement of new peoples towards the wealth and stability of the imperial frontier, and their constant feed into the empire by one means or another, may have created quite a dynamic flux of population in the immediate 'barbarian' hinterland, disguised by the names Romans used for various foreign peoples.
In other words, were the people the Romans called the Chamavi in the 4th century necessarily descended from the earlier people of the same name? How about the Frisii, the Chatti, or the Batavi? Our evidence in most cases is too thin to permit any assumption, I think.

Ethnogenesis is a difficult concept. For instance I think that the Goths originated as a group only when they arrived at the borders of the Empire. The Franks on the other hand probably saw litle to no change during the 3rd to 5th century and only began that change after Clovis' kingdom was formed? The Anglo-Saxons again formed only as a recognisable group during the 7th century, long after they had arrive in Britain. Bulgarians and Bavarians again were a mix of newcomers and present Roman provincials forming a group that had never been there before. 
All different leaves of the same tree. 

I would not refer to a 'supertribe' as a for of ethnogenesis, but rather a new form of accepted organisation and cooperation without a fixed set of rules. 

@Chamavi - nobody knows, because the Romans were notoriously bad at identifying their neighbours. When it came to callingf the Cimbri/Teutones 'Germanic' or calling the Franks 'Celts' or the Goths 'Scythians' (I'm referring to that 'Byzantine' princess of course).