Islam in the Ottoman Empire
Sunni Islam was the official religion of the Ottoman Empire. The highest position in Islam, caliphate, was claimed by the sultan, after the defeat of the Mamluks which was established as Ottoman Caliphate. The sultan was to be a devout Muslim and was given the literal authority of the caliph. Additionally, Sunni clerics had tremendous influence over government and their authority was central to the regulation of the economy. Despite all this, the sultan also had a right to the decree, enforcing a code called Kanun in Turkish. Additionally, there was a supreme clerical position called the List of Sheikh-ul-Islams of the [Ottoman Empire|Sheykhulislam]. Minorities, particularly Christians and Jews but also some others, were mandated to pay the jizya, the poll tax as mandated by traditional Islam.
Governance
Before the Tanzimat, the ruling institution, also known as the Muslim millet, was known as the Bab-ı Meşihat, the office of the Sheykhulislam. Other names used were the Bâb-ı Fetvâ, Meşîhat Dairesi or the Şeyhülislâm Kapısı.
Sunni Islam
Since the founding of the Ottoman Empire, Ottoman law and religious life were defined by the Hanafi madhab. With respect to creed, the Maturidi school was majorly adhered to, dominating madrassahs so as to apply Islamic principles to fatwas ).
Alevism
Because of their heterodox beliefs and practices, Alevis have been the target of historical and recent oppression. They sided with the Persian Empire against the Ottoman Empire and forty thousand Alevis were killed in 1514 by Ottomans. The Qizilbash of Anatolia found themselves on the "wrong" side of the Ottoman-Safavid border after 1555 Peace of Amasya. They become subjects of an Ottoman court that viewed them with suspicion. In that troubled period under Suleiman the Magnificent the Alevi people were persecuted and murdered.