第6回十字軍
Otto had a legal education, and had joined the Roman "curia" by 1225. His first mission was to England to raise funds for the Sixth Crusade in 1225–1226. In 1227–1228, he undertook his first embassy to Frederick II, Holy Roman Emperor. In 1229–1231, he travelled extensively through France, the Low Countries, Germany, Denmark and Norway on Papal business. In 1232–1233, he undertook his second embassy to Frederick II.