The Fall of Constantinople (Greek: Ἃλωσις 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 army of the Ottoman Empire on 29 May 1453. The Ottomans were commanded by the then 21-year-old Ottoman Sultan Mehmed the Conqueror, 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.
The capture of Constantinople (and two other Byzantine splinter territories soon thereafter) marked the end of the Byzantine Empire, a continuation of the Roman Empire dating to 27 BC, an imperial state lasting for nearly 1,500 years.The Ottoman 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. After the conquest, Sultan Mehmed II transferred the capital of the Ottoman Empire from Edirne to Constantinople.
It was also a watershed moment in military history. Since ancient times, cities had used ramparts and city walls to protect themselves from invaders, and Constantinople’s substantial fortifications had been a model followed by cities throughout the Mediterranean region and Europe. The Ottomans ultimately prevailed due to the use of gunpowder (which powered formidable cannons).
The conquest of the city of Constantinople and the end of the Byzantine Empire was a key event in the Late Middle Ages which also marks, for some historians, the end of the Middle Ages.