Former empire centred in Anatolia. It was named for Osman I (1259–1326), a Turkish Muslim prince in Bithynia who conquered neighbouring regions once held by the Seljuq dynasty and founded his own ruling line c. 1300. Ottoman troops first invaded Europe in 1345, sweeping through the Balkans. Though defeated by Timur in 1402, by 1453 the Ottomans, under Mehmed II (the Conquerer), had destroyed the Byzantine Empire and captured its capital, Constantinople (now Istanbul), which henceforth served as the Ottoman capital. Under Selim I (r. 1512–20) and his son Süleyman I (the Magnificent; 1520–66), the Ottoman Empire reached its greatest peak. Süleyman took control of parts of Persia, most of Arabia, and large sections of Hungary and the Balkans. By the early 16th century the Ottomans had also defeated the Mamluk dynasty in Syria and Egypt; and their navy under Barbarossa soon seized control of much of the Barbary Coast. Beginning with Selim, the Ottoman sultans also held the title of caliph, the spiritual head of Islam. Ottoman power began to decline in the late 16th century. Ottoman forces repeatedly besieged Vienna. After their final effort at taking the Austrian capital failed (1683), that and subsequent losses led them to relinquish Hungary in 1699. Corruption and decadence gradually undermined the government. In the late 17th and 18th centuries the Russo-Turkish Wars and wars with Austria and Poland further weakened the empire, which in the 19th century came to be called the sick man of Europe. Most of its remaining European territory was lost in the Balkan Wars (1912–13). It sided with Germany in World War I (1914–18); postwar treaties dissolved the empire, and in 1922 the sultanate was abolished by Mustafa Kemal Atatürk, who proclaimed the Republic of Turkey the following year. See alsoJanissary; Turk; Young Turks.