The Medieval History of Italy
The middle ages was a traumatic time for the area we now as Italy. It was not a unified single country and was broken up into many independent city-states, provinces of other empires and republics.
During this period many foreign powers controlled large areas of the country. The Holy Roman Empire controlled large parts of northern Italy. The Byzantine Empire for a short period controlled the area around Calabria and Naples, before the Normans, who subsequently lost out to an emerging Sicilian line, who in turn were replaced by an Aragonese line, took it from them.
All threw this the power of the Papacy ebbed and flowed. To the north city states/ republics sprang up. Milan and Genoa on the northeastern coast and the established city-state of Venice continued to play an important part in maritime trade.