Despite heavy casualties during the battle of Kosovo (1389) against a broad alliance of the Balkan peoples led by Serbian lord Lazar and battle of Nicopolis (1396) against European Crusaders led by Jean of Never, Sigismund I of Hungary and Mircea I of Wallachia, Ottoman empire continued to expand under the leadership of sultan Yildirim Bayezid I. To the east new empire under amir Timur (Tamerlane) was on the rise and as the borders of two empires touched, the war was inevitable. The battle of Ankara of 1402 was one of the biggest fought between the Muslim empires. At the same time, results of this massive battle impacted Ottoman, Timurid, Byzantine empires and changed the course of the history of Europe, Asia, Middle East and Balkans.
