The Hundred Years' War

The first few decades of the war were favorable to the English. In 1346 at Crecy, the cream of French nobility was decimated by English archers. In 1356, King John the Good was taken prisoner at Poitiers. The Treaty of Bretigny-Calais freed the king but ceded Aquitaine to the English, which was from then on ruled by the formidable Black Prince.

In 1368, Magne de Castelnaud, sole heiress of Castelnaud, married Nompar de Caumont. This was a major event for Castelnaud, as the Caumonts would subsequently continue to be proprietors of the castle until the Revolution. During the War, the Caumonts were often in the English camp. Henry IV, King of England, named Nompar de Caumont his seneschal for Agen.