The history of Italy in the Middle Ages can be roughly defined as the time between the collapse of the Western Roman Empire and the Italian Renaissance. Late Antiquity in Italy lingered on into the 7th century under the Ostrogothic Kingdom and the Byzantine Empire under the Justinian dynasty, the Byzantine Papacy until the mid 8th century. The "Middle Ages" proper begin as the Byzantine Empire was weakening under the pressure of the Muslim conquests, and most of the Exarchate of Ravenna finally fell under Lombard rule in 751. From this period, former states that were part of the Exarchate and were not conquered by the Lombard Kingdom, such as the Duchy of Naples, became de facto independent states, having less and less interference from the Eastern Roman Empire. Lombard rule ended with the invasion of Charlemagne in 773, who established the Kingdom of Italy and the Papal States in large parts of the Northern and Central Italy. 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. In the 11th century, in the Northern and Central parts of the country, began a political development unique to Italy, the transformation of medieval communes into powerful city-states, many of them, modelled on ancient Roman Republicanism. Cities such as Venice, Milan, Genoa, Florence, Siena, Pisa, Bologna among others, rose to great political power, becoming major financial and trading centers. These states paved the way for the Italian Renaissance and ultimately the "European miracle", the resurgence of Western civilization from comparative obscurity in the Early Modern period. After the three decades of wars in Lombardy between the Duchy of Milan and the Republic of Venice, there was eventually a balance of power between five emerging powerful states, which at the Peace of Lodi formed the so-called Italic League, on the initiative of Francesco I Sforza, bringing relative calm for the region for the first time in centuries. These five powers were the Venetian Republic, the Republic of Florence, the Duchy of Milan and the Papal States, dominating the northern and central parts of Italy and the Kingdom of Naples in the south. The precarious balance between these powers came to an end in 1494 as the duke of Milan Ludovico Sforza sought