The Ottoman Empire was founded by a family descended from the Kayı, one of the 26 Oghuz Turkic tribes who had conquered Anatolia in the 11th century. Under the reign of Osman I (Ataman) (`Uthman عُثْمان in Arabic which will give Ottoman in French, as well as the Turkish name Osmanlı given to his dynasty), while the Seljuk Empire is decomposing, this tribe will begin its extension.
In 1299, Osman I conquered the Byzantine city of Bilecik and this date generally marks the beginning of the Ottoman Empire. Until his death in 1324, Osman I conquered several other Byzantine towns and strongholds, as well as some of the neighboring Turkish settlements.
His successors continued his policy of expansion. The Ottoman Empire conquered Gallipoli, its first European territory, in 1347, then spread across the Balkans. In 1389, he won a decisive victory at the Battle of Kosovo Polje in Serbia (or Battle of the Field of Blackbirds), ending the existence of the Albanian kingdom. Serbia was definitively annexed by the Ottomans after the fall of Smederevo in 1459. In 1453, commanded by Sultan Mehmet II, he seized Constantinople and put an end to the Byzantine Empire. The Empire then gradually established its suzerainty over the entire Muslim part of the Mediterranean world.
The Ottoman sultans saw their titulature enriched in the 15th century with the old Turkish title of khan, then that of Caliph in the 16th century, that is to say successor of Muhammad and head of the Muslim community (Oumma). Their control over their land varies; the distant provinces of Tunis and Algiers, for example, only formally recognize his power. Others, like the Romanian principalities of Wallachia, Moldavia and for a time Transylvania, have been autonomous since the 15th century-16th century, paying just a tribute.
The Empire also has significant Christian populations in the Balkans and Anatolia. He also recruited by force his main military corps, that of the janissaries (an alteration of the Turkish yeniçeri “new soldier”), established in the 14th century by Sultan Orhan. But very many poor Christians (Slavs, Greeks, Armenians, etc.) switch to Islam in order to no longer pay the haraç (tax on non-Muslims) and become Turks:as such, the Turks have European ancestry. that the Turkic speakers of Central Asia do not have.