Kingdom of the Lombards
Leading an army including Bavarians, Gepidae, and Saxons, as well as the non-Germanic Bulgars, the Langobardi invade Italy in 568 AD. They quickly capture the entire peninsula with the exception of Rome (now in ruins and supporting a population of 20,000 compared to 450,000 at its peak) and Ravenna, which the Byzantines manage to hold.
The Kingdom of the Lombards, with its capital at Pavia, rules over Italy for more than 200 years. It is truly barbarian in custom compared with the Odoacer’s kingdom and the Ostrogoth Kingdom. The system is highly decentralized, with the dukes each having practical sovereignty in their territories. A code of laws were not written down until 643, and was merely a codification of the oral legal tradition. Romans were viewed as conquered enemies who had no rights and forced to work as surfs—tied to the land they farmed and obligated to give up a third of the produce to the Lombards, who were thus exempted from agricultural work.
“After the Lombard invasion, the popes (for example, St. Gregory) were nominally subject to the eastern emperor, but often received little help from Constantinople, and had to fill the lack of stately power, providing essential services (such as food for the needy) and protecting Rome from Lombard incursions; in this way, the popes started building an independent state.” -Wikipedia