The House of Montfort was a French noble family, who reigned in the Duchy of Brittany from 1365 to 1514. It was a cadet branch of the Breton House of Dreux, itself a branch of the House of Dreux; it was thus ultimately part of the Capetian dynasty. It shouldn't be confused with the older House of Montfort which ruled as Counts of Montfort-l'Amaury and were the female line ancestors of this royal house.
It succeeded the Brittany branch of the House of Dreux, invoking already in 1341 a right to succeed John III, Duke of Brittany. A war ensued, ultimately won by Montforts in 1364.
The dynasty was succeeded by Valois family, first Claude, the daughter of Montfortine duchess Anne, and then Claude's sons. Already from the time of Duchess Anne's marriage, however, the duchy was gradually subsumed to the French state, in practice, so it can be said that French central government succeeded the Montforts.
Rise to power
Count John of Montfort (1295 1345) was the sole surviving son of Yolande of Dreux, Countess of Montfort suo jure (and dowager queen of Scotland) from her second marriage to Arthur II, Duke of Brittany. John inherited in 1322 Montfort-l'Amaury from his mother. However, he was only a younger son of the Duke, who had several older sons from his first marriage. John only received some appanage in Brittany, and his maternal inheritance, a countship, was a much more important possession.
However, his eldest half-brother, John III, Duke of Brittany, was childless in spite of his three marriages. Duke John III died in 1341, and his duchy's nobles proclaimed Countess Joan of reigning duchess. She was the daughter of the late Guy de Bretagne, comte de Penthi vre, Duke John III's younger full brother, and thus John III's full niece.
John of Montfort however invoked both the principle of Salic Law (allowing only males to succeed) and the principle of proximity of blood (as used earlier e.g. by John I of England against Arthur of Brittany), having himself proclaimed Duke John IV. This led to the Breton War of Succession, a part of the Hundred Years' War. His patron in this quest was king Edward III of England. The rivals, Duchess Joanna and her husband Charles of Blois were supported by the Valois kings of France. John IV died without accomplishing his objective of becoming sole ruler of Brittany, but his wife Joanna of Flanders continued the fight in the name of their son John V, Duke of Brittany (1339/40-99) who ultimately got the upper hand in the strife.
In the midst of the conflict, in 1352, the Estates of Brittany ( tats de Bretagne) were established. They would develop into the Duchy's parlement.
Ruling as dukes
When the peace was sealed in 1365, it was stipulated that the Montfort branch will succeed in Brittany restricted to the Salic Law and in the case of their male line going extinct, the heirs of Joanna of Penthi vre will succeed the last male Montfortist duke. The Blois-Penthi vre family received more estates in Brittany as partial compensation.
Brittany kept autonomous, actually rather independent, although continuously giving lip service to French sovereignty. After the Breton War of Succession, Brittany still had links with the English through the Earldom of Richmond, until the Wars of the Roses.
John V, Duke of Brittany was deserted by his nobles in 1473 and left for exile in England. Louis, duke of Anjou, brother of the French king, and a son-in-law of the deposed Penthi vre Duchess Joanna, was appointed lieutenant-general of Brittany by the king, who in 1378 sought to annex Brittany to France, which provoked the Bretons to recall John V from exile.
The second Treaty of Gu rande (1381) established Brittany's neutrality in the Anglo-French conflict, although John continued to make homage to King of France.
In 1420, John VI, Duke of Brittany was kidnapped by Olivier de Blois, count of Penthi vre, son of Joanna of Penthi vre. John's wife, Joan of France besieged the rebels and set free her husband, who confiscated the Penthi vre's goods.
According to the succession order enacted, in 1457 Duke Peter II was succeeded by his elderly uncle Arthur de Richemont instead of his sister Isabelle de Bretagne-Montfort (who married into the Laval family and from whom the future Chabot branch of the Rohan (family) descends).
In 1465, Francis II took the county of Penthi vre from its heiress, Nicole de Bretagne-Blois, thus again undermining the rival family's position in Brittany.
However, the last male Montfort, Francis II, Duke of Brittany (died in 1488) prepared for succession by his daughter Anne of Brittany - thus, the first female Montfort rulership abrogated the rights of genealogically more senior Penthi vre family (Catholics) as well as those of Rohan family (future Huguenots).
In the last years of Francis II, French warred against the Breton and Brittany was defeated in 1488—the last duke of independent Brittany was forced to submit to a treaty giving the King of France the right to determine the marriage of the Duke's daughter, a young girl 12 years old, the heir to the Duchy.
The independence of Brittany waned under the French dominion. Anne was forced to marry Charles VIII of France, but their children did not survive. When Charles died, Anne had to marry his distant cousin and successor, Louis XII of France.
End of dynasty
Jean de Brosse (died 1502), grandson of Nicole de Blois the aforementioned, asserted their claim to the duchy when the last male duke Francis II died. Previous Montfortine rulers of Brittany had however by confiscations and exilings much weakened the Penthi vre family's resources in the duchy and Anne succeeded her father in the administration which wanted to protect Brittany's position to external predators.
Anne died in 1514, leaving her inheritance to her elder daughter Claude of France (died 1524), who was proclaimed Reigning Duchess, but it was under the tactical dominion of Anne's widower king Louis (Claude's father, died 1515), and afterwards Claude's husband king Francis. The Montfort family continued only in female line, as nominally and titularly first Claude and then her sons Fran ois, Dauphin of France and after him the future Henry II of France were proclaimed Dukes of Brittany.
Claude's widower Francis I of France incorporated the duchy into the Kingdom of France in 1532 through the Edict of Union between Brittany and France, which was registered with the Estates of Brittany.