The arrangement by which the Ottoman Empire governed its non-Muslim subjects as self-administering religious communities — chiefly Greek Orthodox, Armenian, and Jewish — each headed by its own clergy and answerable to the sultan for taxes, law, and order within the group. Neither modern toleration nor simple oppression, it was a hierarchical accommodation that granted communal autonomy and protection of worship while keeping non-Muslims legally subordinate. The tidy three-millet scheme often described as ancient was largely a nineteenth-century construction, and the system broke apart as nationalism turned religious communities into rival nations.
When the Ottomans took Constantinople in 1453, the conquering sultan did not abolish the Greek Orthodox Church. He appointed its patriarch. Mehmed II installed a churchman as the head of all the empire's Orthodox Christians, and began to rule many of them through their own clergy. Only over time did this grow into the broader pattern by which non-Muslim communities handled much of their own worship, family law, schooling, taxation, and discipline. The patriarch became an Ottoman official. The strangeness of this is easy to miss. A Muslim ruler who had just stormed the greatest Christian city on earth chose to keep the church running and to govern through it, not around it. That decision was not tolerance in the modern sense, and it was not equality. It was a way of ruling a religiously divided empire by letting each faith govern its own.