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Why did Otto IV invade Frederick II’s Italian lands?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Frederick II
Frederick II Frederick II, bust, c. 13th century; in the collection of the Museo Provinciale Campano, Capua, Italy.

Otto IV invaded the Italian lands of Frederick II because he did not intend to honor his previous commitments to the papacy. After being crowned Holy Roman emperor in 1209, Otto refused to concede to the church all the territories the papacy had been claiming from the empire.

Furthermore, despite having previously agreed not to claim suzerainty over the Kingdom of Sicily—a policy intended by Pope Innocent III to prevent the reunion of the German and Sicilian crowns—Otto broke his word. He occupied Tuscany and subsequently invaded the mainland portion of Frederick’s kingdom in 1210, conquering southern Italy. This aggression led to his excommunication by the Pope and prompted an assembly of princes to declare him deposed in favor of Frederick II.1