Mehmed II amalgamated the old Byzantine administration into the Ottoman state. He first introduced the word Politics into Arabic "Siyasah" from a book he published and claimed to be the collection of Politics doctrines of the Byzantian Caeasars before him. He gathered Italian artists, humanists and Greek scholars at his court, kept the Byzantine Church functioning, ordered the patriarch to translate the Christian faith into Turkish and called Gentile Bellini from Venice to paint his portrait. He was extremely serious about his efforts to continue the Roman Empire, with him as its Caesar, and came closer than most people realize to capturing Rome and conquering Italy. Mehmed II also tried to get Muslim scientists and artists to his court in Constantinople, started a University, built mosques e.g. the Fatih Mosque, waterways, and the Topkapı Palace.
Mehmed II's reign is also well-known for the religious tolerance with which he treated his subjects, especially among the conquered Christians, which was very unusual for Europe in the Middle Ages. However, his army was recruited from the Devshirme. This group took Christian subjects at a young age. They were split up: those regarded as more able were destined for the sultans court, the less able but physically strong were put into the army or the sultan's personal guard - the Janissaries.
Within the conquered city, Mehmed established a millet or an autonomous religious community, and he appointed the former Patriarch as essentially governor of the city. His authority extended only to the Orthodox Christians of the city, and this excluded the Genoese and Venetian settlements in the suburbs, and excluded the coming Muslim and Jewish settlers entirely. This method allowed for an indirect rule of the Christian Byzantines and allowed the occupants to feel relatively autonomous even as Mehmed II began the Turkish remodeling of the city, eventually turning it into the Turkish capital, which it remained until the 1920s.
Mehmed II spoke seven languages (including Turkish, Greek, Hebrew, Arabic, Persian and Latin) when he was 21 years old (the age at which he conquered Constantinople). After the fall of Constantinople, he founded many universities and colleges in the city, some of which are still active. Mehmed II is also recognized as the first Sultan to codify criminal and constitutional law long before Suleiman the Magnificent (also "the Lawmaker" or "Kanuni") and he thus established the classical image of the autocratic Ottoman sultan (padishah). Mehmed II's tomb is located at Fatih Mosque in Istanbul; the Fatih Sultan Mehmet Bridge is also named after him.
Mehmed II's Firman on the Freedom of the Bosnian Franciscans
"I, the Sultan Khan the Conqueror,
hereby declare the whole world that,
The Bosnian Franciscans granted with this sultanate firman are under my protection. And I command that:
No one shall disturb or give harm to these people and their churches! They shall live in peace in my state. These people who have become emigrants, shall have security and liberty. They may return to their monasteries which are located in the borders of my state.
No one from my empire notable, viziers, clerks or my maids will break their honour or give any harm to them!
No one shall insult, put in danger or attack these lives, properties, and churches of these people!
Also, what and those these people have brought from their own countries have the same rights...
By declaring this firman, I swear on my sword by the holy name of Allah who has created the ground and sky, Allah's prophet Mohammed, and 124.000 former prophets that; no one from my citizens will react or behave the opposite of this firman!"
This oath firman, which has provided independence and tolerance to the ones who are from another religion, belief, and race was declared by Mehmed II the Conqueror and granted to Angjeo Zvizdovic of the Franciscan Catholic Monastery in Fojnica, Bosnia and Herzegovina after the conquest of Bosnia and Herzegovina on May 28th of 1463. The firman has been recently raised and published by the Ministry of Culture of Turkey for the 700th anniversary of the foundation of the Ottoman State. The edict was issued by the Sultan Mehmed II the Conqueror to protect the basic rights of the Bosnian Christians when he conquered that territory in 1463. The original edict is still kept in the Franciscan Catholic Monastery in Fojnica.
It is one of the oldest documents on religious freedom. Mehmed II's oath was entered into force in the Ottoman Empire on May 28, 1463. In 1971 the United Nations published a translation of the document in all the official U.N. languages.