August 3rd , 1379
John IV the Conqueror KG (in Breton Yann IV, in French Jean IV, and traditionally in English sources both John of Montfort and John V) (1339 – 1 November 1399), was Duke of Brittany and Count of Montfort from 1345 until his death and 7th Earl of Richmond from 1372 until his death.
Son of Duke of Brittany
He was the son of John of Montfort and Joanna of Flanders. His father claimed the title Duke of Brittany, but was largely unable to enforce his claim for more than a brief period.
Title Disputed
Because his father’s claim to the title was disputed, with only the English king recognizing it, the subject of this article is often numbered in French sources as “John IV” and his father as simply “John of Montfort” (Jean de Montfort), while in English sources he is known as “John V”. However, the epithet of “The Conqueror” makes his identity unambiguous.
Having achieved victory with English support (and having married into the English royal family), Duke John IV was constrained to confirm several English barons in positions of power within Brittany, especially as controllers of strategically important strongholds in the environs of the port of Brest, which gave the English military access to the peninsula, and which took revenue from Brittany to the English crown.
This English power-base in Brittany was resented by the Breton aristocrats and the French monarchy, as was John’s use of English advisers. However, John IV declared himself a vassal to king Charles V of France, not to Edward III of England. Nevertheless, 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 IV was unable to muster military support against King Charles V, who took the opportunity to exert pressure over Brittany. Without local support, in 1373, he was once more forced into exile to England.
However, King Charles V made the mistake of attempting to completely adjoin the duchy of Brittany to France. Bertrand de Guesclin was sent to make the duchy submit to the French king by force of arms in 1378.
Invited Back
The Breton barons revolted against the takeover and invited Duke John IV back from exile in 1379. He landed in Dinard and took control of the duchy once more with the support of local barons.
An English army under Thomas of Woodstock, 1st Duke of Gloucester, landed at Calais and marched towards Nantes to take control of the city. However, John IV subsequently reconciled with the new French king, Charles VI of France, and paid off the English troops to avoid a confrontation.
He ruled his duchy thereafter in peace with the French and English crowns for over a decade, maintaining contact with both, but minimizing open links to England.
Château de l’Hermine
Between 1380 and 1385, John IV built the Château de l’Hermine (Castle of Hermine) in Vannes, which became a defensive fortress and dwelling for the Dukes of Brittany. He built it in order to benefit from the central position of the city of Vannes in his duchy.
In 1397, Duke John IV finally managed to extricate Brest from English control by using diplomatic pressure and financial inducements
