As the thirteenth century progressed the military orders were often embroiled in the struggle between the Papacy and the Holy Roman Emperors. The Popes, the spiritual leaders of Christendom, demanded obedience from the rulers of Europe, which was seldom granted. Indeed emperors such as Frederick II, a man of great learning and ambition, was frequently at odds with the Papacy and was not above making war against Pope Gregory IX when pressed. For his...