Between 1489 and 1506 the castle was significantly expanded by Konstanty Ostrogski, who made it a modern fortress, one of the strongest in the area. After 1566 Dubno was part of the Volhynian Voivodeship of the Lesser Poland Province of the Polish Crown. During the Polish-Russian War of 1605–1618 in 1617, Prince and future King Władysław IV Vasa resided in the city.