Charles' illness created a power vacuum that eventually led to the Armagnac–Burgundian Civil War between supporters of his brother, Duke Louis I of Orléans, and the royal dukes of Burgundy. Isabeau shifted allegiances as she chose the most favorable paths for the heir to the throne. When she followed the Armagnacs, the Burgundians accused her of adultery with Louis of Orléans; when she sided with the Burgundians, the Armagnacs removed her from Paris and she was imprisoned. In 1407, John the Fearless, duke of Burgundy, assassinated Orléans, sparking hostilities between the factions. The war ended soon after Isabeau's eldest son, Charles, had John the Fearless assassinated in 1419—an act that saw him disinherited. Isabeau attended the 1420 signing of the Treaty of Troyes, which decided that the English king should inherit the French crown after the death of her husband, Charles VI. She lived in English-occupied Paris until her death in 1435.