Timur's victory at Ankara was a masterstroke of military strategy. His victory precipitated twelve years of turmoil in the Ottoman Empire and allowed him to begin campaigns against Ming China. His stated intention in dethroning the Ottoman sultan was to reassert Seljuk authority, which is why he didn't assimilate the western Ottoman holdings into his kingdom. What if his victory at Ankara was not as decisive (perhaps Beyazid escapes), and determined Ottoman resistance developed in Lycia or Ionia which incited Timur to march his armies all the way across the Anatolian peninsula? Could the Ottomans wage a successful guerilla campaign against the Mongols? Would Timur even let himself get tied down with such a war? If he manages to conquer the entire peninsula, would he bother campaigning in the east (he doesn't have much longer to live, if he lives as long as he does in OTL)?