I've been rereading Caesar's Commentaries and came across a passage where the Germanic Suebian king Ariovistus claimed to have intricate knowledge of the political atmosphere and factions in the city of Rome; he tells Caesar that many Roman elites sent agents to him and that they would be grateful if Ariovistus had Caesar killed. As well, during the course of his book, we hear that tribes on the other side of Gaul or in Britain hear about Caesar's campaigns and prepare for military action. We often have the impression that 'barbarian' peoples lurked around in the woods, ignorant of the Mediterranean world, until they collided with it during migrations or invasions.
This got me thinking about how information networks would have functioned beyond the boundaries of Roman and Hellenistic civilizations; how safely could a Roman (or Gallic, Germanic etc.) agent travel to the court of a Germanic king on the Rhine or even further beyond? How long would it have taken? Was it exceptional for Ariovistus to gain information about Roman political intrigue by direct dispatches? How extensive were these networks - did they only reach the most significant powers in pre-Roman temperate Europe or did they extend to smaller communities as well?
I don't expect all of my questions to be answered but I'd appreciate any contribution!
Well, as you have no doubt noticed there are two real characteristics to the way Caesar draws his opponents: one is that they are characters with motivations, and occasionally given to speeches about how they will humiliate Rome (and thus need to be corrected by Caesar) and two is that he tends to "flatten" his enemies so that they all seem intricately connected, which has the side effect of making it entirely reasonable that a war started to halt migration near modern Lyon took him to Britain. So I think it is entirely reasonable to argue that Caesar's portrayal of the Gauls as all interconnected and in communication was a literary device serving a political purpose.
That being said, the material culture of the time shows that there were pretty extensive networks of exchange among the different Gauls. This even includes the construction of fairly sophisticated roads (or at least well worn tracks). Perhaps more significantly, they were capable of raising large armies to oppose Caesar in relatively short amounts of time--this requires extensive networks of political power and, of course, communication.
I think readers of history always underestimates the amount of informal communications that far predate any sort of official actions of governments, or recognition by written sources.
Consider tin. When you look at all the ancient sources of tin available (and tin is pretty critical to the bronze age), almost none of the major deposits are anywhere near what we would consider a center of civilization. So where did Egypt, Mesopotamia, Hattusa, Mycenea, China, India and all those other civilizations get their tin from?
Intuitively, these civilizations likely established trade relations with peoples far beyond their spheres of influences, and these peoples are the ones who mined and supplied the tin. Who were these people they trade with? Who maintained the routes? How reliable were they? No one really knows, since these peoples left no records and very few relics. But consider that even in such a distant, distant past, civilizations transported vast amounts of ore from far away regions in a time that predates any named civilizations in the tin-producing areas, and such trade must've regular in order to sustain the vast amounts of bronze being produced.
If trade and movement was so regular and "easy" in the Bronze age, it's not really surprising for it to have been even easier in Roman times. The truth is, trade routes and exchange can far predate records of them, and I wouldn't be surprised if the Germans and Gauls had numerous roads and routes that connected them to Italy and each other for centuries before Caesar was even born. But understandably, records of these are absent, so we may never really know the specifics of them.