This late 14th century monarch left a regency council including the Marquis of Villena to rule Castile in his absence, and in July 1385 marched his army with French cavalry through Ciudad Rodrigo into Portugal, only to be crushed at Aljubarrota. Which Castilian king led that ill-fated 1385 invasion?

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Accepted Answer

John I of Castile. John I of Castile (reigned 1379–1390) failed to seize the Portuguese crown through his marriage to Beatrice of Portugal. His crushing defeat at Aljubarrota by the outnumbered Portuguese army secured the House of Aviz's rule and confirmed Portugal's independence for centuries to come.