Ottoman's Constantinople Invasion

Something that was mentioned during the Ottoman Empire reading was the fall of Constantinople. The brief comment about the Ottoman siege on Constantinople in Strayer's Ways of the World left me wondering, how was it that such a great capitol was taken over this easily by the Ottomans? 

 This once prosperous capitol of the Byzantine Empire was conquered by the Ottoman Empire during April 5, 1453 through May 29, 1453.  It was a really well planned out attack that the Ottomans led, and the army protecting constantinople was greatly outnumbered. 

The seizer of constantinople took everyone by surprise, because the Muslims weren't the biggest threat to anyone. It was usually the Europeans that started all of the wars between themselves and the Muslims but now this Turk powered Ottoman Empire was relentless and overpowering. They started by first setting up forts along Dardanelles, a neighboring city to Constantinople, and then all at once they had the 80,000 to 200,000 men march to constantinople. The army protecting Constantinople was greatly outnumbered, as they only totaled to 7,000 men, while the Ottomans had 80,000 to 200,000 men. The majority of the Ottomans started by firing at the walls, while a small number of them went of to seize the less populated areas of Constantinople. The plans of the Ottomans to simple get in by firing at the walls did not work at all, and at one point the Ottomans tried to peacefully deal with the situation, and they offered to stop the conquest if the city was given to them. Then when this offer was denied by the Byzantine Empire, a massive wave of Ottomans charged at the walls, but they did not manage to enter the great city. After that wave, the city of Constantinople was hit by a second wave of Ottomans, and this wave did manage to breach a section of the walls. Shortly after that, the Ottomans discovered an unlocked gate, and they quickly flooded the city, ending the seizer. This picture here show the flood of the Ottomans into Constantinople. And that is how the Ottomans managed to take over this very powerful city of Constantinople.