Romans vs \"Barbarians\". Could someone explain...

[Robert Vermaat]

The big tribal confederations of the 4th and 5th centuries became possible because of the poulation increase east of the Rhine. Strategically, the later Roman commanders were probably caught flat-footed and surprised by the size of the migratory groups that came from what they had long considered "the middle of nowhere." Really, it's no wonder the limitanei and other border forces were overwhelmed, because they had grown accustomed to fending off bandits and small warbands.
The Romans, like Jerry Seinfeld, would have wondered "who aaaare these people?"

I'm sorry but where did you find that?
The Romans of course knew fully well what was happening east of the Rhine, why on earth would they not know that? Relations existed, wars were fought, why would germania be a 'terra incognita'? Barbarian groups were resettleld all the time as a result of Roman troops being wasted in civil wars, in which hundreds of thousands of Germans were hired as short-term mercenaries. A pretender emperor could (and ofen did) send a lieutenant to the border regions with a big sack of gold and promises, to hire a s many waariors as were available on short notice. Surly they knew what numbers lived on the opposite of the Rhine!

Your scenario makes me think of those old school plates which show endless lines of ox-drawn carts filled with fur-clad barbarians.. We know this did not happen, and Gaul was never overrun by large groups of immigrants either.. By far the most barbarians which settled the Empire were settled there with full knowledge of and cooperation with the Roman government.

The big confederations seem to have sprung into being by the 3rd century as a result of them being pressed together between a well-defended border and pressure of groups to the east. A development in the social system allowed for many group to work together, but they were never 'one people'. The Franks for instance consisted of a dozen or more competeing groups until Clovis while the Goths were never one, not even under Alaric. They could act together if needs arose, but they fell apart immediately after the leaders of these groups deemed it a better idea.

The limitanei collapsed locally because so many were drafted into the field armies and they were never meant to withstand large invasion forces anyway - that's what the field armies were meant to do.