Vladislav III or (Polish) Władysław III Jagiełło
King of Poland and Hungary, was the son of King Vladislav II of Poland, whom he succeeded in 1434, aged 10; six years later he was elected and crowned as King Vladislas I of Hungary. At the urging of Pope Eugenius IV and with the assistance of János Hunyadi, Vladislav mounted a crusade against the Ottomans. In 1443 his army defeated the forces of Murat II at Niş (then in Bulgaria, now in Serbia) and in the treaty that followed Vladislav regained a substantial amount of territory. He then violated the terms of peace by renewing hostilities, and on 10 November 1444 was killed when his army was defeated at the battle of Varna (Bulgaria).