Mehmed II
Mehmed II (March 30, 1432 – May 3, 1481; nicknamed el-Fatih, 'the Conqueror') was the sultan of the Ottoman Empire for a short time from 1444 to 1446, and later from 1451 to 1481.
Mehmed brought an end to the Byzantine Empire by capturing Constantinople in 1453 (during the well-known Siege of Constantinople), and other Byzantine cities left in Anatolia and the Balkans. The invasion of Constantinople and successful campaigns against small kingdoms in the Balkans and Turkic territories in Anatolia bestowed immense glory and prestige on the country and the Ottoman State started to be recognized as an empire for the first time. Mehmed's advance toward the heart of Europe was stopped by the unsuccessful Siege of Nándorfehérvár in 1456, however.
His reign, mostly known for his capture of Constantinople, is also well known for the unusual tolerance with which he treated his subjects, especially among the conquered Byzantines. Within the vanquished city he established a milet or an autonomous settlement, and he appointed the former Patriarch as essentially governor of the city. However, his authority extended only unto the 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 began the Turkish remodeling of the city, eventually turning it into the Turkish capital, which it remained until the 1920s.
As can be guessed from his successful campaign against Otranto in southern Italy and his adopting the title Roman Caesar (Kayser-i-Rüm), he was presumably trying to vitalize the Eastern Roman Empire. For a probably similar reason, he gathered Italian 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 is also recognized as the first sultan to codify criminal and constitutional law long before Suleyman the Magnificent (also "the Lawmaker") and he thus established the classical image of the autocratic Ottoman sultan (padishah). After the fall of Constantinople, he founded many universities and colleges in the city, some of which are still active.
The Osmanli Dynasty ruled the Ottoman Empire from 1281 to 1923, beginning with Osman I (not counting his father, Ertuğrul), though the dynasty was not proclaimed until 1383 when Murad I declared himself sultan. Before that the tribe/dynasty might have been known as Söğüt but was renamed Osmanli in honour of Osman.
The sultan was the sole regent and government of the empire, at least officially. The sultan enjoyed many titles such as Sovereign of the House of Osman, Sultan of Sultans, Khan of Khans, Commander of the Faithful and Successor of the Prophet of the Lord of the Universe. Note that the first rulers never called themselves sultans, but rather beys. See the article on state organisation of the Ottoman Empire for further information on the sultan and the structure of power.
Hereditiary heads of the House of Osman since 1926:
When Mehmed II (the Conquerer) took over Constantinople on May 29, 1453, he committed a coup d'état by replacing the
Emperor of the Roman empire (a.k.a. the Eastern Roman Empire a.k.a. Byzantine Empire) with himself. He took the title Emperor (imparator)and protector of Orthodox Christianity.
He let himself be crowned Emperor by the Patriarch of Constantinople Gennadius Scholarius, whom he protected and whose stature he elevated into leader of all the Eastern Orthodox Christians.
So in addition to being Sultan of the Muslim citisens and Khan of the Turks, he was now also styled Emperor of the Romans.
As emperor of the Romans he laid claim to all the Roman territories and succesfully managed to put most of the Roman territories (except Rome and Italy) under his own control.
