Zbiroh Castle was in the possession of the Luxembourgs from 1333 to 1437. However, for a significant part of this time, it served as a pawn of the Rosenberg family. Zbiroh came into the hands of the Luxembourgs in 1333, when the 17-year-old King and Margrave of Moravia Charles IV. bought it after his return from France and Italy. Due to its advantageous location on the provincial road from Prague to Bavaria (later the imperial road Via Carolina), he used it during his diplomatic trips. He also stayed at the castle several times with his first wife, Blanka of Valois. In 1336, Charles' father, the Bohemian King John of Luxembourg, pledged the castle to the Rosenberg family to repay his war debts. The Rosenbergs took care of the promotion of Zbiroh to a city and gave it the family five-petalled rose as its coat of arms. At that time, Zbiroh was going through a turbulent period of the Hussite Wars, during which the castle was besieged and shelled. The castle returned to the Luxembourgs in 1431, when it was bought back from the mortgage by Charles' son, the Holy Roman Emperor Sigismund of Luxembourg. At his invitation, the papal legate Aeneas Silvius Piccolomini, later the famous Pope Pius II, stayed at Zbiroha.