Rise of the Ottoman Empire
The foundation and rise of the Ottoman Empire is a period of history that started with the emergence of the Ottoman principality in , and ended with the conquest of Constantinople on May 29, 1453. This period witnessed the foundation of a political entity ruled by the Ottoman Dynasty in the northwestern Anatolian region of Bithynia, and its transformation from a small principality on the Byzantine frontier into an empire spanning the Balkans and Anatolia. For this reason, this period in the empire's history has been described as the Proto-Imperial Era. Throughout most of this period, the Ottomans were merely one of many competing states in the region, and relied upon the support of local warlords and vassals to maintain control over their realm. By the middle of the fifteenth century the Ottoman sultans were able to accumulate enough personal power and authority to establish a centralized imperial state, a process which was brought to fruition by Sultan Mehmed II (r. 1451-1481). The conquest of Constantinople in 1453 is seen as the symbolic moment when the emerging Ottoman state shifted from a mere principality into an empire, marking a major turning point in its history.
History of Islam
The Seljuq Turks declined in the second half of the 13th century, after the Mongol invasion. This resulted in the establishment of multiple Turkish principalities, known as beyliks. Osman I, the founder of the Ottoman dynasty, assumed leadership of one of these principalities (Söğüt) at the end of the thirteenth century, succeeding his father Ertuğrul. Osman I afterwards led it in a series of battles with the Byzantine Empire. By 1331, the Ottomans had captured Nicaea, the former Byzantine capital, under the leadership of Osman's son and successor, Orhan I. Victory at the Battle of Kosovo against the Serbs in 1389 then facilitated their expansion into Europe. The Ottomans were established in the Balkans and Anatolia by the time Bayezid I ascended to power in the same year, now at the helm of a growing empire.