may 22, 1453 - The fall of Constantinople to Mehmed II and the Turks.
This event was significant because after ten centuries of war, victory and defeat the Byzantine Empire came to an end when Constantinople was taken into the hands of the Ottoman Turks in May 1453. The destruction of the city sent shock waves throughout Christendom. Another reason this was a significant event was because the initial attcks on the city's ancient but formidible walls failed with heavy casualties,but after attempts to negotiate a surrender came to nothing except attacks at a higher frequency and larger ferocity. Last of all this event was significant because the Turks spread out to sack the city which created devastation and death form the citizens.
Added to timeline:
The fall of Rome.