Charles De Blois, Or De Chatillon, duke of Brittany, died in 1364. He was the nephew of Philip VI. of France, who, anxious to secure his fortune, married him to Jeanne de Penthievre, heiress apparent to the ducal crown of Brittany. But on the death of John III., in 1341, the claim of Jeanne was disputed by John of Montfort, brother of the deceased, who asserted that Brittany could not revert to female sovereigns. Thence arose a war of 20 years' duration, in which the kings of England and of France participated, the former giving assistance to Montfort, while the latter supported Charles de Blois. His cause at first promised to be successful; his competitor died about 1345, whereupon Jeanne of Montfort came boldly forward in behalf of her young son, and displayed such courage, inspired her followers with such enthusiasm, and obtained such assistance from the chivalry of England, that fortune at last declared for her. Charles was killed in battle, and the duchy of Brittany was awarded to young Montfort.