Diego de Acebo was prior of the cathedral chapter of the
Catedral de Santa María de la Asunción in
El Burgo de Osma, where
Dominic of Osma became a
canon. De Acebo was named
Bishop of Osma in 1201. As bishop, he reformed the canonry according to the
Rule of St. Augustine. Accompanied by the future
Saint Dominic, Diego travelled
ad Marchias Daciae (to
Denmark) in 1203 or 1204 to secure a bride for crown prince Ferdinand, son of
Alfonso VIII of Castile. They made a second journey in 1204 or 1205 intending to bring the girl back with them, but found that she had meanwhile died. They returned by way of Rome, where Diego unsuccessfully petitioned
Pope Innocent III to be entrusted with a mission to the northern pagans. Instead, continuing their journey via
Cîteaux, Diego and Dominic began the work of conversion of the
Cathars. In 1206 Bishop de Acebo became the unofficial leader of a papal mission to Languedoc, in southern France. Diego was instrumental in the foundation of
Prouille and took part in the early Cathar-Catholic debates at
Verfeil, and
Montréal, In 1207 he participated in a religious conference with
Durand of Huesca and other Waldenses at
Pamiers which resulted in Durand and his group returning to the Catholic Church. Soon afterwards Acebo was ordered by the Pope to return to his diocese, where he died on 30 December 1207. ==Notes==