The Fall of Constantinople was the capture of the capital city of the Byzantine Empire by an invading Ottoman army on the Sunday of Pentecost, 29 May 1453.
The attackers were commanded by the 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 the Ottoman State from Edirne to Constantinople and established his court there.
The capture of the city (and two other Byzantine splinter territories soon thereafter) marked the end of the Roman Empire, a state which dated to 27 BC, which had lasted for nearly 1,500 years.
The conquest of Constantinople also dealt a massive blow to the defence of mainland Europe, as the Muslim Ottoman armies thereafter were left unchecked to advance into Europe without an adversary to their rear.
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 Medieval period.