The Fall of Constantinople (1453) is universally known as the siege in which Constantinople as a West-controlled city was ultimately conquered by the Ottoman Turks (who were, at the time, considered to be Easterners despite the fact that they were mostly Eurasian than actually Asian).
This event, which lasted for almost a month and a half (fifty-five days), is simply one of the many sieges of Constantinople, all eleven of which aimed the capture of the city – apart from the Fall of Constantinople, only one of these sieges culminated in the defeat of Constantinople, and that would have to be the siege launched by the Crusaders in the year 1204.
Some people have argued that the Crusader siege had, in effect, weakened Constantinople enough so that the last siege of the Ottoman Turks was successful, though it is the general agreement that since the two events were effectively more than two centuries apart, this is not actually practical possibility (although the numerous struggles for the control of Constantinople most definitely contributed to the demise of this city and much of it’s tradition and culture).
The Fall of Constantinople was also successful because at that point, the city has become fractured, with its territories controlled by different Greek monarchies.
True to its name, the Fall of Constantinople effectively ended Constantinople’s existence as a major cultural and socio-political place of power.