Page "Dominican Order" Paragraph 9

He had accompanied as canon Diego de Acebo, Bishop of Osma on a diplomatic mission to Denmark, to arrange the marriage between the son of King Alfonso VIII of Castile and a niece of King Valdemar II of Denmark.

At that time the south of France was the stronghold of the Cathar or Albigensian heresy, named after the Duke of Albi, a Cathar sympathiser and opponent to the subsequent Albigensian Crusade ( 1209 – 1229 ).