Decline and modernization of the Ottoman Empire
Beginning from the late eighteenth century, the Ottoman Empire faced challenges defending itself against foreign invasion and occupation. In response to foreign threats, the empire initiated a period of tremendous internal reform which came to be known as the Tanzimat, which succeeded in significantly strengthening the Ottoman central state, despite the empire's precarious international position. Over the course of the nineteenth century, the Ottoman state became increasingly powerful and rationalized, exercising a greater degree of influence over its population than in any previous era. The process of reform and modernization in the empire began with the declaration of the Nizam-ı Cedid (New Order) during the reign of Sultan Selim III and was punctuated by several reform decrees, such as the Hatt-ı Şerif of Gülhane in 1839 and the Hatt-ı Hümayun in 1856. At the end of this period, marked with 1908, to a degree the Ottoman military became modernized and professionalized according to the model of Western European Armies. The period was followed by the defeat and dissolution of the Ottoman Empire (1908–1922).
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.