the end of June 1324, and military action by the French followed. Edward sent his wife Isabella, who was sister to the French king, to negotiate a settlement. The Queen departed for France on 9 March 1325, and in September was joined by her son, the heir to the throne, Prince Edward (later Edward III of England). Isabella's negotiations were successful, and it was agreed that the young Prince Edward would perform homage in the king's place, which he did on 24 September and so the duchy was returned to the English crown. When France's Charles IV died in 1328 leaving only daughters, his nearest male relative was Edward III of England, the son of Isabella, the sister of the dead king; but the question arose whether she could legally transmit the inheritance of the throne of France to her son even though she herself, as a woman, could not inherit the throne. The assemblies of the French barons and prelates and the University of Paris decided that males who derive their right to inheritance through their mother should be excluded. Thus the nearest heir through male ancestry was Charles IV's first cousin, Philip, Count of Valois, and it was decided that he should be crowned Philip VI of France. Philip believed that Edward III was in breach of his obligations as vassal, so in May 1337 he met with his Great Council in Paris. It was agreed that Gascony should be taken back into Philip's hands, thus precipitating the Hundred Years War between England and France. At the end of the Hundred Years' War, after Gascony had changed hands several times, the English were finally defeated at the Battle of Castillon on 17 July 1453; Gascony remained French from then on. Province of Guyenne and Gascony From the 17th century onwards, the government of Gascony was united with Guyenne. The government of Guyenne and Gascony (), with its capital at Bordeaux, lasted until the end of the Ancien Régime in 1792. Geography Gascony is limited by the Atlantic Ocean (western limit) and the Pyrenees mountains (southern limit); as the area of Gascon language, it extends to the Garonne (North), and close to the Ariège (river) (East) from the Pyrenees to the confluence of the Garonne with the Ariège. The other most important river is Adour, along with its tributaries Gave de Pau and Gave d'Oloron. The most important towns