Timur, a Turco-Mongol from Transoxiana , had built an empire in Central Asia over the years, and became the most powerful ruler in Central Asia since Genghis Khan . He sought to rebuild the once great Mongol Empire. In the 1380s and 1390s, he invaded and conquered parts of Persia , ravaged southern Russia and Ukraine , and invaded India . Although there had been tensions between the Ottomans and Mongols, nothing would warrant a war, until Bayezid demanded tribute from an emir loyal to Timur, which he understood to be personal and a reason for war. In 1400-01 Timur took Sivas from the Ottomans, parts of Syria from the Mamluks, and next directed towards Anatolia. Meanwhile, in 1402, the Ottomans had been campaigning in Europe. Bayezid broke off the blockade of Constantinople and marched to Ankara after Timur again moved his army to the southeast in the summer of 1402.. Was it Bayezid or TImur who did NOT make the first move or take the first action that initially started the war between the Ottomans and Mongols?