English and French Intervention in the Castilian Civil War

Timeline

1. 1351–1354Burgos · Castile-LeónPeter I and his half-brother Henry of Trastámara fell into civil war over conflicts between royal authority and noble interests; Henry fled to France seeking support, while Peter turned to England for an alliance.
2. 1355–1367Navarre · NavarreFrance dispatched commanders such as Bertrand du Guesclin to lead mercenaries in support of Henry; England sent the Black Prince on an expedition, defeating Henry at the Battle of Nájera in 1367 and restoring Peter to the throne, though the campaign proved costly.
3. 1368–1369Montiel · Castile-La ManchaAfter Peter broke his promises of rewards to the Black Prince, his position collapsed; with du Guesclin's assistance, Henry defeated and killed Peter at Montiel, ascending the throne as Henry II, and Castile shifted into the French camp.