From its origin as a small stronghold built by the ancient Illyrian tribe Dalmatae, it developed into a fortress in the 15th century, during the reign of Bosnian feudal lord Hrvoje Vukčić Hrvatinić.

[6] In 1406, king Ladislaus of Naples gifted Prozor Fortress, at that time Castrum Werhlychky, as a center of Vrlička župa to the Hrvoje Vukčić.

[7][8] Hrvoje Vukčić Hrvatinić was most powerful Bosnian nobleman and magnate of his time,[9] and carried a title of "Grand Duke of Bosnia, Knyaz of Donji Kraji, and Duke of Split" (later Herzog of Split), and now he was made by Ladislaus his "deputy for this Dalmatian territory, calling him his Vicar General for the regions of Slavonia (in partibus Sclavonie)".

At the beginning of the 15th century, Hrvoje Vukčić fortified and strengthened the Prozor Fortress over the Vrlika valley to defend inhabitants from the invasion by the Ottoman Empire.

[8] 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.

When wealthy Prince Ivaniš Nelipić, the last male member of Frankopan's illustrious clan, died in 1434, the problem of inheritance became acute.

In spite of the legality of this bequest, and his consent to the marriage upon request of the late Ivaniš Nelipić, king Sigismund denounced the testament and demanded that Frankopan turn over to him the legacy of his wife's inheritance.

[12] The Prozor Fortress was expended while it was owned by Hrvoje Vukčić Hrvatinić at the end of 14th and early 15th centuries from the small stronghold built by the Illyrian tribe of Dalmatae.