Prior to being excommunicated the first of several times, Holy Roman Emperor Frederick II had planned to go on a crusade. However, an epidemic waylaid him and a large part of his army, delaying the conquest. As a result, he was excommunicated by Pope Gregory IX. He eventually went on the postponed crusade and became king of Jerusalem. With Italy as the center of his power, Frederick, a religious skeptic, was in frequent conflict with the papacy. Frederick wrote the first book on what subject? Discuss (http://forum.thefreedictionary.com/postst29691_Holy-Roman-Emperor-Frederick-II-Is-Excommunicated--1227-.aspx)
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Dont know much about about him.