The Battle of Trancoso was fought on 29 May 1385 between the Kingdom of Portugal and the Crown of Castile. Following the coronation of João of Aviz, John I of Castile sent an army into the Portuguese region of Beira in retaliation for Portuguese defiance, where they committed all the kinds of atrocities. The city of Viseu was pillaged and burned, but when the Castilians were returning to Castile with their plundered loot and the prisoners they had taken, a Portuguese army met them, dismounted and assumed a defensive formation. The Castilians exhausted themselves in attack but ended up being utterly routed, with very high casualties among their ranks, and with six of their seven captains killed. The Portuguese released all those taken captive by the Castilians and recovered all the pillage