Peter IV

(born Sept. 5, 1319, or Sept. 15, 1317, Balaguer, Catalonia—died Jan. 5, 1387, Barcelona) King of Aragon (1336–87). He took the Balearic Islands and Roussillon from Majorca (1343–44), defeated the Aragonese nobles (1348), and became duke of Athens and Neopatras (1380). He waged war against Castile (1356–66) but failed to gain any territory; after 1369 France favoured Castile over Aragon. Peter tried to maintain neutrality in the Hundred Years' War, and he quarreled with his heir, the future John I, who became the tool of French intrigues.

Source: Encyclopedia Britannica