The Fall of Constantinople (, ; Conquest of Istanbul) was the capture of the capital of the Eastern Roman (Byzantine) Empire by an invading army of the Ottoman Empire on 29 May 1453. The Ottomans were commanded by 21-year-old Ottoman Sultan Mehmed II, who defeated an army commanded by Byzantine Emperor Constantine XI Palaiologos. The conquest of Constantinople followed a 53-day siege that had begun on 6 April 1453.