In 1203, what area was a stronghold of the Cathar?
In 1203, Dominic joined Prior Diego de Acebo on an embassy to Denmark for the monarchy of Spain, 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). Dominic was fired by a reforming zeal after they encountered Albigensian Christians at Toulouse.