Medeival/Renaissance Italian political question

[husker9.2]

I don't have great resources here in the USA but this period in Italian history has always fascinated me. Why were there so many city states? Especially in the Po River valley.

And maybe more importantly why didn't the local power's, Venice, Milan, Genoa, and especially the Siculo Normans conquer the entire region? All were a military force too be reckoned with, especially Sicily, who would have had significantly more resources at their disposal than the rest.

So why is this?

[konny]

And maybe more importantly why didn't the local power's, Venice, Milan, Genoa, and especially the Siculo Normans conquer the entire region? All were a military force too be reckoned with, especially Sicily, who would have had significantly more resources at their disposal than the rest.

You said it yourself: All of major the northern Italian petty states were comparable strong, what would explain why none of them was able to unite the entire region.

The Norman Sicilian kingdom, during its short history, never did expand into northern Italy, for various reasons.

Northern Italy (save for Venice) in fact legaly was a part of the HRE, and as long as the emperors were strong they exercised power over those lands. Of course, they had to fight a lot to do so, but all Medieval kings were constantly challanged in all of their realms.

The collapse of the Staufian empire in 1250 indeed opened the road to independence in northern Italy because the following emperors gave up any attempts across the Alps, while southern Italy became a battlefield of the various claimants on the vacant Sicilian throne (until then a Staufian kingdom too) for the next centuries.