...Nantes. Initially, the conflict had been an internal Breton dispute, but it soon became entangled in the larger Anglo-French conflict of the Hundred Years’ War (1337–1453).

The Truce Between England and France and the Looming Renewal of War

• The Hundred Years’ War had begun in 1337, but in 1341, a temporary truce between England and France delayed open hostilities.
• However, both sides expected the war to resume in June 1342, when the truce was set to expire.
• This political climate made Brittany’s internal war even more consequential, as both France and England had an interest in controlling the duchy.

Philip VI Intervenes: Charles of Blois Becomes the French Candidate

• When rumors reached Philip VI that John of Montfort had received English envoys, the French king quickly took direct action.
• Charles of Blois—already the preferred heir of the late Duke John III—was officially designated as the French-backed claimant.
• This turned the Breton Succession Crisis into a proxy war, making Brittany a key battleground in the wider Anglo-French struggle.

John of Montfort Aligns with Edward III of England

• Whatever Montfort’s initial intentions, Philip VI’s intervention forced him into an alliance with Edward III.
• By 1341, John of Montfort had little choice but to support Edward III’s claim to the French throne, aligning himself with the English cause.
• This alliance guaranteed English military support, setting the stage for an English-backed intervention in Brittany.

Implications for the War

• The Breton War of Succession (1341–1365) was now part of the larger Hundred Years’ War, with:
  • Charles of Blois backed by France.
  • John of Montfort supported by England.
• As the truce between England and France neared its expiration, both sides prepared for renewed hostilities, with Brittany as a key theater of conflict.

John of Montfort’s rapid conquest of Brittany in 1341 ensured that the Breton Succession Crisis would become a proxy war, further entangling France and England in one of the most protracted conflicts of medieval Europe.