 At the beginning of the 15th century, Hrvoje Vukčić fortified and strengthen the Prozor Fortress over the Vrlika valley to defend inhabitants from the invasion by the Ottoman Empire.After 1416, and Hrvoje Vukčić death, his son Balša Hercegović was unable to hold Prozor Fortress, which then passed to Ivaniš Nelipić, and later to Ivan Frankopan.In 1421, king Sigismund donated Vrlika with the Prozor Fortress to Mihača Nikolin Vitturi, but Ivaniš Nelipić refused to handover the fortress.