Stalemate in Brittany: Olivier de Clisson’s Military Buildup and Duke John IV’s Attempt on Quimperlé (1377–1378)

By 1377–1378, Brittany remained a contested region in the ongoing struggle between French-backed Olivier de Clisson and English-backed Duke John IV. While Clisson had amassed military forces in southern Brittany, John IV attempted to capture Quimperlé, but both sides were ultimately restrained by a truce between the Kings of France and England.

Olivier de Clisson’s Military Preparations

• As Constable of France, Olivier de Clisson strengthened French forces in Brittany, concentrating his efforts in the southern part of the duchy.
• His goal was to drive out English influence completely, particularly by forcing John IV out of his remaining strongholds.
• However, his ability to mobilize these forces was curtailed by the diplomatic situation.

Duke John IV’s Attack on Quimperlé

• Meanwhile, John IV, still loyal to England, attempted to capture the town of Quimperlé, likely as part of his broader strategy to reassert control over Brittany.
• His campaign faced difficulties, as his support from the English crown was weakened by political instability in England following Edward III’s death in 1377.

The Truce Between France and England (1377–1378)

• A truce between King Charles V of France and King Richard II of England prevented major military action in Brittany.
• This truce frustrated Clisson’s efforts, as he was unable to launch a full-scale offensive despite his military buildup.
• John IV was similarly unable to push his campaign further, leaving Brittany in a state of uneasy stalemate.

Impact and Consequences

• The truce prevented immediate conflict but did not resolve the underlying tensions in Brittany.
• Clisson remained a powerful force, waiting for an opportunity to resume hostilities once the truce expired.
• John IV’s position remained precarious, as he struggled to regain control over his duchy while still being reliant on English support.

The military deadlock in Brittany (1377–1378) left the struggle between Clisson and John IV unresolved, setting the stage for future conflicts once the fragile truce between France and England collapsed.