What caused the Hundred Years' War?
There were a number of causes of the One Hundred Years War. Foremost was the question of inheritance and titles among kings. Due to complicated family lineage and ties between the French and English royal families, King Edward III of England was also a vassal of King Philip VI of France. The origin of this inconvenient situation began in 1066, when William, Duke of Normandy, seized the English throne. His descendants continued to rule England while still technically being vassals of the French kings.
Threatened by having another king hold a fief in his realm, Philip moved to occupy Edward's land in Guyenne in 1337. Edward responded by claiming succession to the French throne and invading Flanders, where the English had trade...
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The Hundred Years' War was caused by two notable issues.
King Charles IV of France died sonless, leaving no male heir that could legally inherit the throne. King Edward III of England was the nephew of King Charles. Edward's mother was Isabella of France. He tried to stake a claim to the French throne on the account that he was a rightful male heir. The French denied this claim. Philip VI of France said that under the Salic Law, men were unable to inherit property or thrones through their mother.
Additionally, France and England were economic (or trade) rivals. The English depended on the wool trade from Flanders, and France attempted to intervene in their trade agreement to export wool.
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