Battle of Castillon
The Valois kings of France, claiming supremacy over Aquitaine, granted the title of duke to their heirs, the Dauphins, during 1345 and 1415: John II (1345–50), Charles VII (1392?–1401), and Louis (1401–15). French victory was complete with the Battle of Castillon of 1453. England and France nominally remained at war for another 20 years, but England was in no position to continue its campaign, due to its escalating internal conflicts. The Hundred Years' War was formally concluded with the Treaty of Picquigny of 1475. With the end of the Hundred Years' War, Aquitaine returned under direct rule of the king of France and remained in the possession of the king. Only occasionally was the title of "duke of Aquitaine" granted to another member of the dynasty, and then as a purely nominal distinction.