John, King of England treatment of many of England's most powerful nobles. Although both John and the barons agreed to the " peace treaty in 1215, neither side complied with its conditions. Civil war broke out shortly afterwards, with the barons aided by Louis of France. It soon descended into a stalemate. John died of dysentery contracted whilst on campaign in eastern England during late 1216; supporters of his son Henry III went on to achieve victory over Louis and the rebel barons the following year. Contemporary chroniclers were mostly critical of John's performance as king, and his reign has since been the subject
Isabella of Castile, Duchess of York elder sister, Constance (d. 1394), who after the death of their father in 1369 claimed the throne of Castile. Isabella accompanied her sister to England, and on 11 July 1372, at about the age of 17, married John of Gaunt's younger brother, Edmund of Langley, 1st Duke of York, fifth son of King Edward III and Philippa of Hainault, at Wallingford, Oxfordshire, as part of a dynastic alliance in furtherance of the Plantagenet claim to the crown of Castile. According to Pugh, Isabella and Edmund of Langley were 'an ill-matched pair'. As a result of her indiscretions, including an affair