Olivier de Clisson’s Shift to the French…

Olivier de Clisson’s Shift to the French Crown and the Construction of Josselin Castle (1369–1373)

By 1369, Olivier de Clisson, a former ally of the pro-English Duke John IV of Brittany, had begun to shift his allegiance to King Charles V of France. His involvement in French military planning, his land acquisitions in Normandy and Brittany, and his formal recognition of French suzerainty over Josselin all marked his definitive break with the Montfortist cause.

Olivier de Clisson’s Role in French Invasion Plans (Spring 1369)

• In 1369, Clisson advised Charles V on a planned French invasion of England, emphasizing:
  • The dangers of winter storms in the Channel, given the French fleet’s weaknesses.
  • The importance of launching an invasion in the spring, when weather conditions were more favorable.

The Failed Siege of Saint-Sauveur-le-Vicomte and Diplomatic Maneuvering (August 1369)

• Later in August 1369, Clisson attempted to capture Saint-Sauveur-le-Vicomte in Normandy, which was held by the English.
• However, he was forced to abandon the siege and instead negotiated on behalf of Duke John IV with King Charles V.
• It was at this stage that Charles V secured Clisson’s full allegiance, rewarding him with lands in Normandy.

Acquisition of Josselin and Final Break with John IV (1370)

• In 1370, Clisson exchanged his Norman lands with his cousin, the Count of Alençon, for the lordship of Josselin in Brittany.
• He then formalized his shift in loyalty by signing a charter recognizing the suzerainty of the King of France over Josselin, despite the territory being in the heart of Brittany.
• Duke John IV expressed strong disapproval, seeing Clisson’s actions as a betrayal of Breton independence.

Construction of Josselin Castle (1370)

• Having acquired Josselin, Clisson began constructing an imposing fortress, featuring:
  • Eight massive towers, designed for defensive and symbolic purposes.
  • A strategic stronghold to secure his power in Brittany, reinforcing his new loyalty to the French king.
• The castle would later become one of the most formidable fortresses in Brittany, reflecting Clisson’s wealth and growing status under French rule.

Clisson Joins Bertrand du Guesclin in War Against England (1370–1373)

• In the same year, Clisson formally joined Bertrand du Guesclin, the newly appointed Constable of France, and fought alongside him in French campaigns against the English.
• Among these campaigns was the Siege of Brest (1373), a critical battle in the French efforts to retake English-held strongholds in Brittany.

Impact and Legacy

• Clisson’s defection to the French Crown significantly weakened English influence in Brittany, as he was one of the most capable Breton commanders.
• His construction of Josselin Castle symbolized his commitment to French rule and his break with Duke John IV.
• By aligning with Bertrand du Guesclin, he played a key role in France’s renewed military efforts, marking the beginning of a major French counteroffensive in the Hundred Years’ War.

Olivier de Clisson’s shift to the French side in 1370 was a turning point in Breton and French politics, reinforcing France’s influence in Brittany and helping to drive back English forces during the later stages of the war.