The Ottoman Empire was an empire that lasted from 1299 to 1922. With Constantinople as its capital city, it was in many respects an Islamic "successor" to the Eastern Roman (Byzantine) Empire.
The Ottoman Empire was, in theory, tolerant towards Christians and Jews. Mehmed II allowed the local Christians to stay in Constantinople after conquering the city in 1453, and in 1461 Sultan Mehmed II established the Armenian Patriarchate of Constantinople. Previously, they were seen as heretical.
In terms of policy matters, the empire's relationship with the Greek Orthodox Church was largely peaceful. In practice, however, Christians faced discrimination in every level of society. In addition to this
Voluntary conversion to Islam was often greeted by Ottoman authorities, and it was no secret that Muslim authorities perceived Islam as a higher form of belief. In addition to this, conversation to Islam meant that those who were formerly Christians did not have to worry about paying the jizyah, a tax that was levied on non-Muslim citizens.
As a result, many Christians in Asia Minor converted en masse for purely economic reasons.