Otto IV, 1175?–1218, Holy Roman emperor (1209–15) and German king, son of Henry the Lion, duke of Saxony. He was brought up at the court of his uncle King Richard I of England, who secured his election (1198) as antiking to Philip of Swabia after the death of Holy Roman Emperor Henry VI. Civil war in Germany ensued. The murder of Philip (June, 1208), who had just been recognized by Pope Innocent III as king, although not Otto's work, revived his cause; he won over the princes by submitting to a new election (Nov., 1208). By the charter of Speyer (Mar., 1209), Otto confirmed his earlier acknowledgment (1201) of the papacy's rights to the Papal States and his promise of aid in upholding papal suzerainty over Sicily. He also conceded the freedom of episcopal elections and the unrestricted right of appeal to the pope. However, no sooner was he crowned emperor (Oct., 1209) at Rome than he reverted to the Hohenstaufen policy of dominance over Italy. He seized (1210) the lands left to the church by Matilda of Tuscany. Only when he invaded Apulia and prepared to attack Sicily, however, did Innocent III excommunicate him (1210). Prompted by the pope and by King Philip II of France, some of the German nobles revolted and elected the Hohenstaufen, Frederick of Sicily (later Holy Roman Emperor Frederick II), as king. In the ensuing war Otto was supported by the nobles of the Lower Rhine and of the northeast, as well as by his uncle King John of England, but he was defeated (1214) at Bouvines by Philip II of France. The pope declared him deposed in 1215.
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