Breton Civil War, 1341

French invasion of Brittany
Part of the Breton Civil War
Citizens of Nantes paying homage to John of Montfort and Jeanne of Flanders
Date May 1341 – February 1342 Location Province of Brittany Result Indecisive
Belligerents
House of Blois France	House of Montfort
Commanders and leaders
Charles of Blois John, Duke of Normandy	John of Montfort Jeanne of Flanders
Strength
7,000+	Unknown

The opening events of the Breton Civil War took place in 1341 when a French royal army intervened in a dynastic dispute between two claimants to the duchy of Brittany. Brittany was a province of France, but was treated in many ways as an independent principality. When John III, Duke of Brittany (r. 1312–1341), died on 30 April 1341, title to the duchy was claimed by both his niece, Joan of Penthièvre, and his younger half brother, John of Montfort. Joan's claim was through her husband, Charles of Blois, a nephew of the King of France, Philip VI (r. 1328–1350). A complicating factor was the war between France and England which had broken out in 1337. (This was the Hundred Years' War, which lasted until 1453.) A truce was in effect, which was due to expire in June but was extended to June 1342.

It was generally assumed that Joan's claim would prevail and that Charles would become the new duke. But John acted quickly and installed friendly garrisons in most of the towns and castles of Brittany by August. He discussed the possibility of a military treaty with English emissaries, but made no move towards effecting one. Rumours of this reached Philip, causing him to turn against John and in September Charles was recognised as the new duke. John refused to give way and Philip sent an army nominally commanded by his son to impose Charles. Within a month John had been defeated and was a prisoner. His wife, Jeanne of Flanders, sent the ducal treasury west to Brest, took command of her husband's field army, stormed the town of Redon and then moved to the small but strongly walled town of Hennebont. She despatched a senior counsellor to encourage English intervention, set up her two-year-old son, also John, as the faction's figurehead and heir to his father's claim to the duchy, and waited on events. This was the start of the Breton Civil War which was to last 24 years.