(July 20, 1402), military confrontation in which forces of the Ottoman sultan Bayezid I were defeated by those of the Central Asian ruler Timur (Tamerlane) and which resulted in the collapse of Bayezid's empire.

While challenging the Christian world in the West, Bayezid had annexed the Anatolian Turkmen principalities and posed as heir to the Seljuqs of Anatolia. Meanwhile, Timur claimed suzerainty over these same principalities and gave refuge to the Turkmen princes defeated by Bayezid. The sultan, on his part, protected Timur's enemies, the Kara Koyunlu (“Black Sheep”) and Jalāyirid rulers. Exasperated, Timur seized Sivas in central Anatolia (August 1400); Bayezid retaliated by capturing Timur's protégé, the ruler of Erzincan in eastern Anatolia. Finally the two rivals met at Çubukovasi, near Ankara, where Bayezid's Turkmen vassals deserted to Timur and the Ottomans were overwhelmed. The sultan himself was captured; he died in captivity in 1403.