1366-1369: The First Castilian Civil War, Companies, and Strategic Realignment

Charles V’s reign was shaped beyond France as well. Castile was strategic: its fleet could threaten English communications and influence Aquitaine. At the same time, France still struggled with ransom burdens and the devastation caused by the Great Companies.

The Castilian civil war offered a dual solution: weaken England indirectly and move mercenary bands out of the kingdom.

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⛪ Avignon, “Crusade” Framing, and Funding

Mercenary violence also threatened papal territories near Avignon. A campaign framed as a crusading expedition into Iberia allowed converging interests. Charles V tasked Bertrand du Guesclin with assembling and directing companies out of France.

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👑 1366: Henry of Trastamara’s Advance

The intervention moved quickly, and Henry of Trastamara was crowned in April 1366. This gave Charles V the prospect of a friendly Castilian regime.

But Peter of Castile prepared a return with support from the Black Prince and Navarrese networks.

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🏴 1367: Nájera and English Overstretch

The Black Prince crossed through Navarre and defeated Henry at Nájera (April 3, 1367). Du Guesclin was captured. Yet the English victory was costly, and Peter could not honor promised payments.

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🧾 Financial Blowback in Aquitaine

Unpaid and expensive campaigning strained English power and aggravated fiscal tensions in Aquitaine, helping prepare political rupture there.

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🗡️ 1369: Montiel and Durable Alliance

Henry and Du Guesclin regained momentum. Peter was defeated and killed at Montiel, and Henry II secured the Castilian throne. The Franco-Castilian alignment later proved decisive at sea, notably at La Rochelle (1372).

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🧠 To Remember

• Castile was an indirect but decisive front.
• Nájera was a tactical defeat with strategic long-term benefits for France.
• Montiel created the alliance that helped transform the war balance.