<P> The Fall of Constantinople ( Greek : Ἅλωσις τῆς Κωνσταντινουπόλεως , Halōsis tēs Kōnstantinoupoleōs ; Turkish : İstanbul'un Fethi Conquest of Istanbul ) was the capture of the capital of the Byzantine Empire by an invading Ottoman army on 29 May 1453 . The attackers were commanded by the then 21 - year - old Sultan Mehmed II , who defeated an army commanded by Emperor Constantine XI Palaiologos and took control of the imperial capital , ending a 53 - day siege that had begun on 6 April 1453 . After conquering the city , Sultan Mehmed transferred the capital of his Empire from Edirne to Constantinople , and established his court there . </P>
who did the ottoman empire defeated in 1453
an army commanded by Emperor Constantine XI Palaiologos