Otto IV

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Otto IV (1174–1218) ( Otto of Brunswick) Holy Roman Emperor (1198–1215). A member of the Guelph family, Otto antagonized the powerful Pope Innocent III by his invasion of Italy against the Hohenstaufen King Frederick I (later Emperor Frederick II). With Innocent's support, Frederick was elected king (1212) by the German princes, and supported by Philip II of France. Philip defeated Otto at Bouvines in 1214, forcing Otto to retire.