Novo Brdo was the last Serbian town to remain standing during the first invasion. In 1439 the capital of Smederevo fell and Serbia resisted until finally Novo Brdo fell in 1441. Novo Brdo was by treaty restored to the Serbs in 1443. The fortress (named in Turkish "Nobırda") came under siege for forty days by the Ottomans, before capitulating and becoming occupied by the Ottomans on 1 June 1455. This event is described by Konstantin Mihailović from Ostrovica near Novo Brdo, who was taken by the Ottomans along with some 300 other boys to be trained as Janissaries. All of the higher ranking Serbian officials were executed after the castle fell, with the younger men and boys being taken captive to serve in the Ottoman Army, and some 700 young Serbian women and girls being taken to be wives to Ottoman commanders.