 In 862, Louis's brother Lothair II sought to annul his marriage to Teutberga, as she had failed to bear him any children.The local bishops had blessed the annulment and Lothair's subsequent remarriage, but in November 863, Pope Nicolas summoned the bishops to Rome and excommunicated them for their violation of ecclesiastical law.The bishops fled to Louis's court and pleaded their case, resulting in the Emperor laying siege to the Holy See in January 864.