Battle of Aljubarrota

Battle context

The Battle of Aljubarrota, fought on 14 August 1385 between the Kingdom of Portugal and the Crown of Castile at São Jorge in central Portugal, between Leiria and Alcobaça, produced a decisive Portuguese victory that settled the dynastic contest at the heart of the 1383–1385 Crisis. John I of Portugal, commanding alongside his Constable Nuno Álvares Pereira and English allies, defeated the substantially larger Castilian force of John I of Castile — supported by Aragonese, French, and Genoese contingents — inflicting casualties of 4,000–5,000 against Portuguese losses of roughly 1,000 from a force of 6,600 facing an army of 31,000. The scale of the disparity in losses underscores the completeness of the Castilian defeat. The outcome foreclosed Castilian claims to the Portuguese throne, ending the succession crisis that had destabilized Portugal since 1383 and securing John I's position as king. In doing so, Aljubarrota preserved Portuguese independence against absorption into the Castilian dynastic sphere, a result that defined the political configuration of the Iberian Peninsula for the period that followed.