John of Montfort was a notable figure in the 14th century, known for his role as the Duke of Brittany. Born in 1339, he was the son of John III, Duke of Brittany and Joan of Penthièvre. His life was marked by political struggles and conflicts over the ducal title, particularly with the House of Penthièvre. He became Duke in 1341 after a disputed succession, leading to a long civil war known as the Breton War of Succession. John of Montfort's reign was characterized by his efforts to consolidate power and maintain the independence of Brittany from France. He died in 1399, leaving a legacy of resilience in the face of adversity.