Today in History: Frederick II is Excommunicated

On this day (September 29) in 1227, Pope Gregory IX excommunicated Holy Roman Emperor Frederick II for having failed to go on crusade in keeping with his oath. His reign was filled with conflicts with the popes due to his territorial expansion from Germany and Northern Italy to the Kingdom of Sicily (surrounding the papal estates). Frederick had made a good faith effort to go on crusade (his wife, married by proxy, was heiress to the Kingdom of Jerusalem) but he caught ill in an epidemic and was forced to turn back. That was when Gregory excommunicated him. He finally went on crusade the following June but was denied help by the military orders in the Holy Land and the crusader states because he had been excommunicated. (Actually Pope Gregory excommunicated Frederick a second time for going on crusade while excommunicated.) In February 1229 he succeeded in signing a treaty that returned Jerusalem to Christian hands (and was condemned for the “trick”).