The Ottoman Empire began at the very end of the 13th century with a series of raids from Turkic warriors (known as ghazis) led by Osman I, a prince (bey) whose father, Ertugrul, had established a power base in Söğüt (near Bursa, Turkey). Osman and his warriors took advantage of a declining Seljuq dynasty, which had been severely weakened by the Mongol invasions. The Ottoman dynasty continued to expand for several generations, controlling much of southeastern Europe, the Middle East, and North Africa at its peak. Osman’s grandson Murad I laid the foundation for an institutionalized Ottoman state, continued by Murad’s son Bayezid I.