of illness, leaving Yolande, at age 33, in control of the House of Anjou. She acted as regent for her son because of his youth. She also had the fate of the French royal house of Valois in her hands. Her young son-in-law, the Dauphin Charles, was exceptionally vulnerable to the designs of the English King, Henry V, and to his older cousin, John the Fearless, the Duke of Burgundy. Charles' nearest older relatives, the Dukes of Orléans and of Bourbon, had been made prisoners at the Battle of Agincourt and were held captive by the English. With his mother, Queen Isabeau, and the Duke of Burgundy allied with the English, Charles had no resources to support him other than those of the House of Anjou and the smaller House of Armagnac. Following the assassination of John the Fearless at Montereau in 1419, his son Philip the Good succeeded him as Duke of Burgundy. With Henry V of England, he forced the Treaty of Troyes (21 May 1420) on the mentally-ill King Charles VI. The treaty designated Henry as "Regent of France" and heir to the French throne. Following this, the Dauphin Charles was declared disinherited in 1421. When both Henry V of England and Charles VI of France died in 1422 (on 31 August and 21 October, respectively), the Dauphin Charles, at age 19, legitimately became Charles VII of France. Charles' title was challenged by the English and their Burgundian allies, who supported the candidacy of Henry VI of England, the infant son of Henry V and Catherine of Valois, Charles' own sister, as king of France. This set the stage for the last phase of the Hundred Years' War: the "War of Charles VII". In this struggle, Yolande played a prominent role in surrounding the young Valois king with advisers and servants associated with the House of Anjou. She manoeuvred John VI, Duke of Brittany, into breaking an alliance with the English, and was responsible for a soldier from the Breton ducal family, Arthur de Richemont, becoming Constable of France in 1425. Yolande gave early and strong support to Joan of Arc, when others had doubts. Yolande unquestionably practised realistic politics. Using the Constable de Richemont, Yolande was behind the forceful removal of several of Charles VII's advisers. Thus, La Trémoille was attacked and forced from the court in 1433. The contemporary chronicler Jean Juvenal des Ursins (1433–44),