High Quality Content by WIKIPEDIA articles! The Fall of Constantinople was the capture of the capital of the Byzantine Empire, which occurred after a siege by the Ottoman Empire, under the command of Ottoman Sultan Mehmed II, against the defending army commanded by Byzantine Emperor Constantine XI. The siege lasted from Friday, 6 April 1453 until Tuesday, 29 May 1453 (according to the Julian Calendar), when the city was conquered by the Ottomans.