Vast state created by Central Asian Oghuz Turks (or Osmanlis, after the dynastic founder Osman I ) from ca. 1300 to 1923 ; its territories ultimately encompassed southeastern Europe, Anatolia, the Middle East to Iran, and North Africa. Mehmed II conquered Constantinople ( 1453 ), which had been ravaged and depopulated by the Latin Crusaders since 1204 ; he rebuilt and repopulated the city. Thousands of persecuted Jews emigrated from Christian Europe to Ottoman lands at the behest of Sultan Mehmed and the chief rabbi of Edirne, providing substantial support to Mehmed's massive effort to rebuild Istanbul. The reign of Suleyman the Magnificent , 1520 – 66 , marked the peak of Ottoman power and prosperity as well as the highest development of its government, social, and economic systems. Ottoman Islam was a syncretistic system combining the practices and beliefs of Sunnism, Sufism, and indigenous Christianity. Muslims, Christians, and Jews were organized into millets, which were responsible for both religious and secular duties in their communities. The empire eventually weakened due to large-scale corruption and nepotism, overtaxation, and misrule. Extensive reforms were implemented between 1808 and 1909 ; democracy flourished from 1909 to 1918 with an active parliament, multiple political parties, and enactment of major secular and liberal reforms. Austria's annexation of Bosnia and Bulgaria's conquest of east Rumelia encouraged Christian minorities throughout the empire to rebel; the Turkish war for independence ( 1918 – 23 ), led by Mustafa Kemal Atatürk and Ismet Inono , resulted in the establishment of the Turkish Republic in Anatolia and eastern Thrace.