During the Dark Ages, Italy was invaded by foreign tribes and was divided into several warring city-states and maritime republics, leading to Italy being the location of several wars as the Middle Ages continued. Perhaps the two most famous wars were the wars of the pro-Papal Guelphs and pro-Hohenstaufen Ghibellines from 1156 to 1334 and the Italian Wars of 1494-1559, both of which saw the Papal States fight against intervening foreign powers, in the former case the Holy Roman Empire, while the latter saw the Emperor, the Spanish Empire, the Kingdom of France, and the Kingdom of England scrap over Italian politics. Italy would only be united in 1860, when the Kingdom of Sardinia - with the assistance of Napoleon III of France - reunited northern Italy (which it had seized from the Austrian Empire) with the Kingdom of the Two Sicilies. In 1870, the Italians occupied Rome after the French guards left to fight in the Franco-Prussian War, and Italy became a kingdom. It would become a republic in 1946 after the end of World War II, which had seen the people rise up against fascist Prime Minister Benito Mussolini and the National Fascist Party, and it is currently led by the social democratic Democratic Party of Italy. In 2015, Italy had a population of 60,674,003 people, with most of them 83.3% being Catholic, 12.4% nonreligious, 3.7% Muslim, .2% Buddhist, .1% Hindu, and .3% other religions.