You're probably right, but looking at Germany and most of the region around it, it's clear that a lot of different "tribes" lived in overlapping areas before an

You're probably right, but looking at Germany and most of the region around it, it's clear that a lot of different "tribes" lived in overlapping areas before and after the Roman Empire, at different times... there were the Goths, Vandals, Gauls, Celtics, Suebis, Franks, Synthians, Vikings, "Greeks" (or Helenics), the Rus, Tatars, lots of Slavic tribes that seem to have arrived in Eastern Europe out of "nowhere"... if you include the Iberic Peninsula, Arab peoples dominated for several hundred years, then "disappeared" again in the 15-16th centuries. Most of these completely disappeared (though they obviously left genetic material in the local populations, their culture/language was entirely replaced and mostly forgotten)! Take the Vandals... they seem to have originated in Poland, migrated south pushed by the Mongol raids and later the Goths (themselves coming from Northern Germany or even Scandinavia), ended up in the Iberian Peninsula, then somehow moved even further to Northern Africa... They got their reputation which lives on today (in the word vandalism in case you didn't know) by sacking Rome when the Western Roman Empire had already lost most of its glory, coming from Northern Africa and a few Mediterranean islands, the most import of which was probably Sicily. More recently, the Lithuanian people lost almost all of their territory when the Grand Duchy of Lithuania disappeared (it was subdued by the arch-rivals Russia, Sweden which at the time was nosing around in the area, occupying places like today's Estonia, and the Austrians)... Lithuania only became a country again, and a tiny one at that, after the USSR collapsed, something like 300 years later. In the last couple of centuries the history is even more complex!! We don't notice in a lifetime but the map keeps changing and the previous century was no exception. Where are Yougoslavia and Checkoslovakia now? :D ... did you know that Kyiv changed countries dozens of times over its history? It was capital of the Rus, invaded by the Mongols, incorporated by the Grand Duchy of Lithuania, then Poland, the Russian Empire, then it really went crazy and switched back-forth between the earlier "rulers" and short-lived Ukrainian states multiple times (like 10 times, seriously), was captured by the German army not once, but twice (in WWI and WWII), before kind of stabilizing as part of the USSR, and then finally, a proper Ukrainian state. I was in the area some time ago and it was mind blowing to learn all that.