The Hundred Years’ War had a number of causes, including disagreements over rights to land, a dispute over the succession to the French throne, and economic conflicts. Many of these revolved around the duchy of Aquitaine, a province in southern France that became part of the holdings of the English crown when Eleanor of Aquitaine married King Henry II of England in 1152. French policy in the fourteenth century was strongly expansionist, however, and the French kings resolved to absorb the duchy into the kingdom of France. Aquitaine therefore became a disputed territory.

The immediate political cause of the war was a disagreement over who would inherit the French throne after Charles IV of France, the last surviving son of Philip the Fair, died childless in 1328. Charles IV had a sister — Isabella — but her son was Edward III, king of England. An assembly of French high nobles, meaning to exclude Isabella and Edward from the French throne, proclaimed that, according to French law, “no woman nor her son could succeed to the [French] monarchy.” The nobles passed the crown to Philip VI of Valois (r. 1328–1350), a nephew of Philip the Fair.

In 1329, Edward III formally recognized Philip VI’s lordship over Aquitaine. Eight years later, Philip, eager to exercise full French jurisdiction there, confiscated the duchy. Edward III interpreted this action as a cause for war. He argued, as the eldest directly surviving male descendant of Philip the Fair, that he deserved the title of king of France. Edward III’s dynastic argument upset the feudal order in France: to increase their independent power, many French nobles abandoned Philip VI, using the excuse that they had to transfer their loyalty to a different overlord, Edward III. One reason the war lasted so long was that it became a French civil war, with some French nobles, most important among them the dukes of Burgundy, supporting English monarchs in order to thwart the centralizing goals of the French kings. On the other side, Scotland — resisting English efforts of assimilation — often allied with France.

The governments of both England and France manipulated public opinion to support the war. Kings in both countries instructed the clergy to deliver sermons filled with patriotic sentiment. Royal propaganda on both sides fostered a kind of early nationalism, and both sides developed a deep hatred of the other.

Economic factors involving the wool trade and the control of Flemish towns were linked to these political issues. The wool trade between England and Flanders served as the cornerstone of both countries’ economies; they were closely interdependent. Flanders technically belonged to the French crown, and the Flemish aristocracy was highly sympathetic to that monarchy. But the wealth of Flemish merchants and cloth manufacturers depended on English wool, and Flemish burghers strongly supported the claims of Edward III. The disruption of commerce with England threatened their prosperity.