<Tr> <Td_colspan="2"> <Ul> <Li> Bapheus </Li> <Li> Dimbos </Li> <Li> Catalan campaign </Li> <Li> Prusa </Li> <Li> Pelekanon </Li> <Li> Nicaea </Li> <Li> Nicomedia </Li> <Li> 1st Gallipoli </Li> <Li> 2nd Gallipoli </Li> <Li> Adrianople </Li> <Li> 1st Thessalonica </Li> <Li> Philadelphia </Li> <Li> 1st Constantinople </Li> <Li> 2nd Constantinople </Li> <Li> 2nd Thessalonica </Li> <Li> 3rd Constantinople </Li> <Li> Trebizond </Li> </Ul> </Td> </Tr> <Ul> <Li> Bapheus </Li> <Li> Dimbos </Li> <Li> Catalan campaign </Li> <Li> Prusa </Li> <Li> Pelekanon </Li> <Li> Nicaea </Li> <Li> Nicomedia </Li> <Li> 1st Gallipoli </Li> <Li> 2nd Gallipoli </Li> <Li> Adrianople </Li> <Li> 1st Thessalonica </Li> <Li> Philadelphia </Li> <Li> 1st Constantinople </Li> <Li> 2nd Constantinople </Li> <Li> 2nd Thessalonica </Li> <Li> 3rd Constantinople </Li> <Li> Trebizond </Li> </Ul> <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> <P> The capture of the city (and two other Byzantine splinter territories soon thereafter) marked the end of the Byzantine Empire, a continuation of the Roman Empire, an imperial state dating to 27 BC, which had lasted for nearly 1,500 years . The conquest of Constantinople also dealt a massive blow to Christendom, as the Muslim Ottoman armies thereafter were left unchecked to advance into Europe without an adversary to their rear . </P>

Who did the ottoman empire defeated in 1453