What was the main cause of the Hundred Years' War?

The main cause of the Hundred Years' War was the complex issue of claims to the French throne. The conflict arose primarily from a dispute over which royal family had legitimate rights to the French crown. After the death of Charles IV of France without a male heir, Edward III of England asserted his claim to the French throne based on his maternal lineage. This claim was contested by the Valois dynasty, leading to a series of military confrontations that lasted from 1337 to 1453.

This dynastic struggle was further fueled by various political and territorial ambitions, but fundamentally, it centered around the legitimacy of the English king's claim to rule over France, which set the stage for prolonged warfare and significant shifts in power between England and France as well as wider implications for European politics during that era.