Walk to Canossa
The "Middle Ages" proper begin as the Byzantine Empire was weakening under the pressure of the Muslim conquests, and the Exarchate of Ravenna finally fell under Lombard rule in 751. Lombard rule ended with the invasion of Charlemagne in 773, who established the Kingdom of Italy and the Papal States. This set the precedent for the main political conflict in Italy over the following centuries, between the Pope and the Holy Roman Emperor, culminating with conflict between Pope Gregory VII and Henry IV and the latter's "Walk to Canossa" in 1077.