John of Gaunt III's rule was becoming unpopular due to high taxation and his affair with Alice Perrers, political opinion closely associated the Duke of Lancaster with the failing government of the 1370s. Furthermore, while King Edward and the Prince of Wales were popular heroes due to their successes on the battlefield, John of Gaunt had not won equivalent military renown that could have bolstered his reputation. Although he fought in the Battle of Nájera (1367), for example, his later military projects proved unsuccessful. When Edward III died in 1377 and John's ten-year-old nephew succeeded as Richard II of England, John's influence strengthened.
John of Gaunt Castilians refused to offer battle and the Galician-Anglo-Portuguese troops, apart from time-wasting sieges of fortified towns, were reduced to foraging for food in the arid Spanish landscape. They were harried mainly by French mercenaries of the Castilian king. Many hundreds of English, including close friends and retainers of John of Gaunt, died of disease or exhaustion. Many deserted or abandoned the army to ride north under French safe-conducts. Shortly after the army returned to Portugal, John of Gaunt concluded a secret treaty with John of Trastámara under which he and his wife renounced all claim to the Castilian throne in