Why couldn t Constantinople be conquered?

Why couldn t Constantinople be conquered? ♦Special Thanks to Nikola Jankovic for providing information for this video. ♦Consider supporting the Channel : https://www.patreon.com/Knowledgia ♦Please consider to SUBSCRIBE : https://goo.gl/YJNqek ♦Music Used : Kevin MacLeod - Impact Allegretto Kevin MacLeod - BTS Prolog ♦Script & Research : Skylar Gordon #History #Documentary