The province remained under roman control for at least 15 years and the population of rome was way bigger than the germanic populations, enough to make sure germanics would remain a minority in the empire at best and Germanicus Julius Caesar had an amazing success in restoring the rhine as the border (instead of the previous elbe), under this prospective it seems rome had the means to continue expanding north, and if they indeed expanded north what effect would this have on the later germanic invasions ?
Caesar's conquest of Gaul was made easier by the level of centralization the Gauls already possessed. They had fortified towns (Oppida), an established noble class, and a level of agriculture that could produce excess food. The Romans could co-op the local nobility with Roman luxuries, and supply their troops from allied towns. The Germani, on the other hand, were much more decentralized, with smaller, self-sufficient villages, but no excess. Furthermore, the villages were somewhat mobile, and the Germani possessed little that wasn't transportable. The Germanic nobles were not as susceptible to soft Roman luxuries.
The inability to supply Roman garrisons from Germania meant they had to run supplies from Gaul and Italy. With poor paths into Germania itself, this left the river networks as the main supply lines. The Romans could easily run supplies up and down the Rhine and some of its tributaries, which left them in strong control of the Rhine, Lippe, and Main river valleys. However, the Weser and Elbe rivers empty into the North Sea. This meant a hazardous trip along the coast in the Summer, and no supplies in the winter, forcing the Romans to return to winter quarters on the Rhine and Lippe. Beyond the Elbe, the rivers empty into the Baltic, meaning an impossible trip around Jutland. The summer-only presence of the Romans severely limited their power, and hostile Germanic tribes could always move beyond the Elbe, as the Marcomanni did and it seems during Germanicus' reprisals other tribes did as well.
The Waldgirmes Forum remains show the Romans were making slow progress in trying to settle the Germanic tribes down. With the Germanic disdain for soft Roman luxuries and their distrust of stronger tribal confederation leaders, this would never have been a quick process as it was in Gaul and southern Britannia.
The final decision on the reconquest of Germania lay with Tiberius. While the traditional narrative is that Augustus gave Tiberius a deathbed command to stay within their current borders, this may well be a convenient fiction on the part of Tiberius. Either way, Tiberius had good reasons not to go back. He'd already lost a brother (Drusus) there. The revolt in Illyricum had cost the Romans dearly, in both financial and manpower terms. The manpower cost to the legions was evident in two causes of the legionary revolts on the Rhine: Forced conscription of Roman citizens, and 'stop-loss' of legionary retirements. Furthermore, it was clear that all eight legions now on the Rhine would be needed to retake Germania. Eight legions under Tiberius' popular nephew, Germanicus, was probably more than Tiberius was willing to risk. He reassigned Germanicus and split the legions under two governors.
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