The War of the Keys: The History and Legacy of the Military Conflict Between the Holy Roman Empire and the Vatican

It has been famously pointed out that the Holy Roman Empire was neither holy, nor Roman, but it was also not an empire in the sense people expect when hearing the term. In theory, the emperor was the highest prince in Christendom, and his dominion extended the length and breadth of Western Europe. The empire had been created by the papacy when Pope Leo III famously crowned the supposedly unwitting Charlemagne in Saint Peter's Basilica, intending to recreate the Western Roman Empire. In trut...