843–867: Brittany, Ballon, Jengland, and Treaties

Under Charles the Bald, Brittany moves from a zone “to be held” to a kingdom imposing its conditions. Between 843 and 851, war, raids, and treaties reshape the balance of power in the West.

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🤝 841–843: from an oath to war

In 841, Charles receives the oath of Nominoë, a major figure in Brittany. But as early as 843, hostilities begin: Brittany becomes an active front while the kingdom already faces Vikings and internal tensions.

Charles tries to secure the Loire: he entrusts Bégon with defending the south bank around Nantes, with the installation of a stronghold at the origin of Bouguenais. Divisions in the Frankish camp nevertheless limit the effectiveness of this system.

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⚔️ 845: Ballon

In 845, Nominoë wins the battle of Ballon against Charles. The victory strengthens Breton autonomy and weighs on negotiations.

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📜 846: a first treaty

An agreement in 846 recognises Nominoë as ruler in Brittany. It is not only a military compromise: it is a political status change, acknowledging a more independent Brittany within Carolingian space.

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🧨 849: hostilities resume

In 849, war resumes. Bretons raid West Francia (notably Maine, Anjou, Poitou) and seize Rennes and Nantes. At this moment, Viking pressure and Frankish weaknesses amplify the Breton advantage.

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🏁 851: Jengland and the Treaty of Angers

On 22 August 851, Charles is defeated at Jengland by Erispoë. In September, the Treaty of Angers:

• cedes to Erispoë the counties of Rennes and Nantes as well as the Pays de Retz;
• recognises a Breton royal title in exchange for homage.

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🧩 867: Compiègne and Breton expansion

Under Salomon, the new king of Brittany, Charles must accept further expansion: by the Treaty of Compiègne (867), he concedes the Cotentin and the Avranchin.

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🧠 Key takeaways

• Brittany gains a more autonomous political status between 843 and 851.
• Defeats (Ballon, Jengland) lead to structuring treaties (846, Angers 851).
• Compiègne (867) marks a territorial expansion recognised by Charles.