The Armagnac–Burgundian Civil War

The 1407 murder of Louis of Orléans on the orders of John the Fearless, Duke of Burgundy, split the French aristocracy into two armed camps during the mental incapacity of King Charles VI. The Armagnacs, gathered around the house of Orléans, and the Burgundians fought for control of the royal government, Paris, and the person of the king. The conflict hollowed out the French monarchy precisely when it faced renewed English invasion. With no coherent national military command, France could not field a unified army, a structural weakness exposed at Agincourt in 1415. Burgundy's eventual alliance with England (formalised at Troyes in 1420, which disinherited the Dauphin) turned the civil war into the decisive internal fracture of the late Hundred Years War. The feud was nominally healed only with the Treaty of Arras in 1435, when Philip the Good reconciled with Charles VII, allowing the French recovery that ended the war in 1453.

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