The influence of the Jagiellonian dynasty in Central Europe rose during the 15th century. In 1471, Casimir's son Władysław became king of Bohemia, and in 1490, also of Hungary. The southern and eastern outskirts of Poland and Lithuania became threatened by Turkish invasions beginning in the late 15th century. Moldavia's involvement with Poland goes back to 1387, when Petru I, Hospodar of Moldavia sought protection against the Hungarians by paying homage to King Władysław II Jagiełło in Lviv. This move gave Poland access to Black Sea ports. In 1485, King Casimir undertook an expedition into Moldavia after its seaports were overtaken by the Ottoman Turks. The Turkish-controlled Crimean Tatars raided the eastern territories in 1482 and 1487 until they were confronted by King John Albert, Casimir's son and successor.