The Ottomans were led by the Sultan in political matter and the Caliph in religious matters.
Ottomans
Mustafa Kemal Pasha.
No. The Ottomans adopted Islam and today some 99.5% of Turks are at least titularly Muslim.
A Caliph.
The military establishment is one of the attributes that made the Ottomans expand their empire with much success.
The ottomans were Muslim.
Yes it was .
1453
The Sultan.
I am not sure what "the" Islamic Empire is. There have twenty-five or so different Islamic Empires. However, there are some territories that the Ottomans failed to conquer that were part of other Muslim States either concurrently or in times past. Persia, India, Spain, and Indonesia all come to mind.
Christian leaders of the Byzantine Empire viewed the expansion of the Muslim Ottomans with great concern and alarm, as it posed a direct threat to their territories and religious authority. The Ottomans’ advance was seen not only as a military challenge but also as a potential undermining of Christianity in the region. This fear intensified with the fall of Constantinople in 1453, which marked a significant loss for Christendom and was perceived as a catastrophic blow to Christian influence in the region. The Byzantine leaders sought to rally support from Western Europe, but their efforts were largely met with indifference.
The Ottomans