The Ottoman Empire (; ', literally "The Sublime Ottoman State"; Modern Turkish: ' or '; ) was a state that controlled much of Southeastern Europe, Western Asia, and Northern Africa between the 14th and early 20th centuries. It was founded at the end of the 13th century in northwestern Anatolia in the town of Söğüt (modern-day Bilecik Province) by the Turkoman tribal leader Osman I. After 1354, the Ottomans crossed into Europe and with the conquest of the Balkans, the Ottoman beylik was transformed into a transcontinental empire. The Ottomans ended the Byzantine Empire with the 1453 conquest of Constantinople by Mehmed the Conqueror. The Ottoman Empire would very slowly decline until its fall after World War I, in which it sided with the losing Central Powers of the German Empire, the Austro-Hungarian Empire, and Bulgaria.