Proximity from Italy not counting?
He meant Roman Gaul.
I myself have often wondered about this subject. Over time there have been several mass migrations from the steppes pouring into Europe.
Scythians, Sarmatians, Iazyges, Roxalani, Alans, Goths, Huns, Avars, Bulgars, Magyars, Cumans, Kipchaks, Gokturks, Khazars, Pechenegs, and eventually the Mongols.
It's like a revolving door of badasses on horses, each as powerful and penetrating as the next.
So, here's the question. Without Rome, what does the Balkans look like. Well, you've got Dacia. Perhaps it is unified, perhaps it isn't. Depends on a lot of factors. Either way, the Dacians seemed pretty adept at keeping the horse nomads out of their territory and therefore out of the Balkans until the Romans came along and destroyed them. However, even before that, you had Sarmatians and other Iranic tribes sort of going around the Dacians and migrating up the upper Danube into Pannonia. Now, it seems to me that the Dacians were like a kind of cork keeping the flow of nomads from pouring into Europe. But that just seems to damn simple, and inevitably some tribe is going to break them. Will the Dacians assimilate, or continue on as a culture? I can't say.
Insofar as I'm aware, the transition from Iranian steppe tribes to Turkish steppe tribes is a period that presents something of a mystery to archaeologists and historians.