 Complete the following phrase:  After a successful crusade in 144344, which penetrated all the way to Sofia and led to the restoration of the Serbian Despotate under the terms of the Szeged peace treaty, Novo Brdo was returned without a fight to Despot Đurađ Branković. Under Đurađs vassal obligations towards the Ottoman sultan, a detachment of cavalry and a company of tunnel diggers from Novo Brdo were sent to Mehmet II 14511481 to aid in his attack on Constantinople, which ended on 29 May 1453 with the 