The Mamluks in Egypt too. They started out as slave troops, who eventually gained so much power and influence that they took control of Egypt, conquered Syria, and even defeated the Mongols at Ain Jalut.
But the Mamluks and Egyptians never become an Empire or Imperial power, not like the Turks. in late Medieval, Ottoman is the patron Caliphate to all Muslim kingdoms (including Muslim kingdoms in South East Asia). In Islam, we cannot have two caliph, there will be only one at one time. So if there are more than one leader in any region, one caliph will become the patron of all others. In late medieval, Ottoman Turk is the strongest of all and the patron of all caliphs, sultan, leader (or whatever they called in own language) If we read history of Islam up to medieval era, it look like we have many separate kingdoms, but actually we are all one kingdom.
The Messenger of Allah (saw) said: "The Muslim Ummah (people) is a unique Ummah (people) among the whole of mankind: Their Land is ONE, their War is ONE, their Peace is ONE, their Honor is ONE and their Trust is ONE."(Ahmed)
The Turks had no good reason to conquer and take over Constantinople except might makes right which is why I hope one day its re conquered by Europeans.
They have reasons, but i don't want to talk about that...and Byzantium/Constantinople/Istanbul will never be conquered again by anyone....and expect Vatican/Rome/Italy will fall soon.... it have been written and it shall be done