John IV, Duke of Brittany

John V the Conqueror (in Breton Yann IV, in French Jean IV) (1339 – November 1 1399), was Duke of Brittany and Count of Montfort, from 1345 until his death.

Numbering

He was son of John de Montfort and Joanna of Flanders. His father claimed the title John IV, Duke of Brittany, but was largely unable to enforce his claim for more than a brief period. Because his father's claim to the title was disputed, the subject of this article has often been numbered John IV, while his father has been referred to as simply "John de Montfort". He is still numbered John IV by some historians and is still more commonly known by that designation (Jean IV) in France.

Conquest

The first part of his rule was tainted by the Breton War of Succession, fought by his father against his cousin Joanna of Penthièvre and her husband Charles of Blois. With French military support Charles was able to control most of Brittany. After his father's death, John's mother took him to England to ask for the aid of Edward III. She was later declared insane and imprisoned in Tickhill Castle in 1343. John was taken in to the King's household afterwards.

John returned to Brittany to enforce his claim, with English help. In 1364, John managed to win a decisive victory against the House of Blois in the Battle of Auray, with the support of the English army. His rival Charles was killed in the battle and Charles's widow Joanna was forced to sign the Treaty Guérande on April 12 1365. In the terms of the treaty, Joanna gave up her rights to Brittany and recognized John as sole master of the duchy.

Power struggles

Having achieved victory with English support (and having married into the English royal family), Jean was contrained to confirm several English barons in positions of power within Brittany, especially as controllers of strategically important strongholds in the environs of Brest. This gave the English a military powerbase in Brittany which was resented the Breton aristocrats and the French monarchy. However, John V declared himself a vassal to king Charles V of France, not to Edward III of England. This gesture did not placate his critics, who saw the presence of rogue English troops and lords as destabilizing. Faced with the defiance of the Breton nobility, John was unable to muster military support against Charles V, who took the opportunity to exert pressure over Brittany. Without support, in 1373 Jean was forced into exile once more in England.

However, Charles V made the mistake of attempting to completely annex the duchy to France. Bertrand de Guesclin was sent to make the duchy submit to the French king by force of arms in 1378. The barons revolted against the annexation and invited Jean V back from exile in 1379. He landed in Dinard and took control of the duchy once more with the support of local barons. Reconciled with the new French king Charles VI, he ruled his duchy thereafter in peace with the French and English crowns for over a decade. He eventually managed with difficulty to extricate Brest from English control in 1397.

Clisson affair

In 1392 an attempt was made to kill Olivier de Clisson, the Constable of France, who was an old enemy of the duke's. John was assumed to be behind the plot, and Charles VI took the opportunity to attack Brittany once more. Accompanied by the Constable, he marched on Brittany, but before he reached the duchy the king was seized with madness. Relatives of Charles VI blamed Clisson, and instituted legal proceedings against him to undermine his political position. Stripped of his status as Constable, Clisson now took refuge in Brittany and was reconciled with John, becoming a close advisor to the duke.

Family

Marriages

John V married three times:

1) Mary Plantagenet (1344–1362), daughter of Edward III of England and Philippa of Hainault;

2) in London in May 1366, Joan Holland (1350–1384), daughter of Thomas Holland, 1st Earl of Kent and

3) at Saillé-près-Guérande on October 2, 1386, princess Joanna of Navarre (1370–1437), daughter of Charles II of Navarre

Joanna was the mother of all his children.

Children

Jeanne of Brittany (Nantes, August 12, 1387 – December 7, 1388)
a daughter (1388)
John VI, Duke of Brittany (1389–1442)
Marie of Brittany (Nantes, February 18, 1391 – December 18, 1446), Lady of La Guerche, married at the Château de l'Hermine on June 26, 1398 John I of Alençon
Marguerite of Brittany (1392 – April 13, 1428), Lady of Guillac, married on June 26, 1407, Alain IX, Viscount of Rohan and Count of Porhoët (d. 1462)
Arthur III, Duke of Brittany (Château de Succinio, August 24, 1393 – December 26, 1458, Château Nantes)
Gilles of Brittany (1394 – July 19, 1412, Cosne-sur-Loire), Lord of Chantocé and Ingrande
Richard of Brittany (1395 – June 2, 1438, Château de Clisson), Count of Benon, Étampes, and Mantes, married in 1423 Margaret d'Orléans, Countess of Vertus, daughter of Louis of Valois, Duke of Orléans
Blanche of Brittany (1397 – aft. 1419), married at Nantes on June 26, 1407 John IV, Count of Armagnac