Middle Ages
Throughout the 14th century, French kings sought to expand their influence at the expense of the territorial holdings of the nobility. They ran into difficulties when attempting to confiscate the holdings of the English kings in southern France, leading to the Hundred Years' War, waged from 1337 to 1453. Early in the war the English under Edward III (r. 1327–77) and his son Edward, the Black Prince (d. 1376), won the battles of Crécy and Poitiers, captured the city of Calais, and won control of much of France. The resulting stresses almost caused the disintegration of the French kingdom during the early years of the war. In the early 15th century, France again came close to dissolving, but in the late 1420s the military successes of Joan of Arc (d. 1431) led to the victory of the French and the capture of the last English possessions in southern France in 1453. The price was high, as the population of France at the end of the Wars was likely half what it had been at the start of the conflict. Conversely, the Wars had a positive effect on English national identity, doing much to fuse the various local identities into a national English ideal. The conflict with France also helped create a national culture in England separate from French culture, which had previously been the dominant influence. The dominance of the English longbow began during early stages of the Hundred Years' War, and cannon appeared on the battlefield at Crécy in 1346.
Duchy of Aquitaine
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.