War of the Breton Succession
Joanna of Flanders ( 1295 – September 1374) was Duchess of Brittany by her marriage to John of Montfort. Much of her life was taken up in defence of the rights of her husband and, later, son to the dukedom, which was challenged by the House of Blois during the War of the Breton Succession. Known for her fiery personality, Joanna led the Montfortist cause after her husband had been captured, and began the fight-back, showing considerable skill as a military leader.