The final fall of the Byzantine Empire was caused by attacks from the Ottomans.
The Byzantine Empire fell, and Islam spread into Eastern Europe. The Byzantine Empire fell in 1453. The main reason of its fall was a significant number of attacks made by the Ottoman Turks. In 1454, Constantinople finally surrendered to them.
The final fall of the Byzantine Empire was accomplished by the siege of Constantinople. Constantinople was one of the most heavily fortified cities in the world, it was defended by 10 thousand men.
Because of this, the siege lasted more than 50 days, the Ottoman empire had 100 thousand men on their side and used a cannon to destroy the walls and enter the city. When the city was taken by the Ottoman Empire it was renamed Istanbul.
