Slavic Northern Italy

I assume with the Slavs in North Italy the Germans are forced out of the peninsula altogether. What's the butterfly effects from there?

More likely they'd merge. I can see some Longobards heading south (possibly leading to linguistic exclaves of Germanic in Benevento Duchy) but it is more likely that the "Slavic" group that migrates is quite sble to absorb pre-existing groups in the first place.
I like Basileus's scenario, though I think that Po Valley and Greater Slovenia will end as separate states with probably slightly different languages (Germani-influenced Slovenian proper, Romance-influenced Padan-Slavic).
 
I think that the Eastern Empire might do better. They would have a stable romanized population. If I remember correctly the northern Balkans had been resettled by people from around the empire. Maybe we would still have Thracians
 
Interesting idea, but a question. How is Venice blocking it?

By naval power, support by Byzantium, and control of the marshlands on the lower Po. In the long run it doesn't preserve independence though, failing to build the historical land possessions, and switching to a mixed Slavic-Romance dialect and subjection of whatever power in possession of the mainland precisely in that era. (Which would be a bad thing for art, by the way. Venice would be less interesting and characteristic, maybe more of an Amsterdam on steroids with a touch of Mediterranean and Balkan).
 
By naval power, support by Byzantium, and control of the marshlands on the lower Po. In the long run it doesn't preserve independence though, failing to build the historical land possessions, and switching to a mixed Slavic-Romance dialect and subjection of whatever power in possession of the mainland precisely in that era. (Which would be a bad thing for art, by the way. Venice would be less interesting and characteristic, maybe more of an Amsterdam on steroids with a touch of Mediterranean and Balkan).

But what naval power does Venice have at this point, what aid can Byzantium spare?
 
But what naval power does Venice have at this point, what aid can Byzantium spare?

Exactly the same it had historically, and it was considerable at that time. Venice's fleet crushed Comacchio and fought the Arabs already in the IXth century, conquered Dalmatia from Narentans around 1000 with Byzantine assent, long dominated the routes to "Rhomania" and the Levant in a struggle with Genoa, Amalfi and Pisa among others since then, and more clearly over Genoa after the Fourth Crusade (Which I assume *here* would not happen, with a Venice relatively weaker by ths time). After the equivalent of OTL War of Chioggia Venetian naval power would be curtailed by the Genoese, meaning the beginning of the end for the Republic, soon to be eclipsed and absorbed by the mainland.
 
Exactly the same it had historically, and it was considerable at that time. Venice's fleet crushed Comacchio and fought the Arabs already in the IXth century, conquered Dalmatia from Narentans around 1000 with Byzantine assent, long dominated the routes to "Rhomania" and the Levant in a struggle with Genoa, Amalfi and Pisa among others since then, and more clearly over Genoa after the Fourth Crusade (Which I assume *here* would not happen, with a Venice relatively weaker by ths time). After the equivalent of OTL War of Chioggia Venetian naval power would be curtailed by the Genoese, meaning the beginning of the end for the Republic, soon to be eclipsed and absorbed by the mainland.

And the Slavic migrations are earlier - more like the 7th century than the 9th.

http://www.angelfire.com/empire/egfroth/BalkanSlavs.html
 
Top