Castile, a medium-sized kingdom with a strong maritime tradition, was plunged into civil war following the death of Alfonso XI in 1349; the conflict between Pedro of Castile and Henry II of Castile became bound up with the wider politics of the Hundred Years' War. With France supporting Henry and his descendants, England exploited opportunities to destabilise the regime. Attempts by John I, Henry's son, to unify Castile and Portugal, resulted in a Portuguese uprising and the intervention of the English John of Gaunt, claiming the Castilian throne by right of marriage. Not until 1387 was the civil war finally concluded, with John of Gaunt accepting a cash settlement. Aragon, a smaller kingdom but with widespread claims to lands across the Mediterranean, also saw internal clashes over dynastic inheritance; Peter IV fought a harsh campaign against his nobles from 1346–9 over his daughter's right to inherit the throne.