Awarded the high honorary title of despot by Byzantine Emperor Manuel II Palaiologos, Lazarević began to wield increasing autonomy in his political decision making.Buoyed by Ottoman reinforcements, Branković set up in Kosovo, along the route through which Lazarević would return from the Adriatic coast to the Serbian interior.While Vuk experienced setbacks fighting Branković's forces, Stefan Lazarević encountered more success in fending off the Ottomans, thereby deciding the battle in his favor.The new political landscape made for closer Byzantine–Serbian cooperation, and in August 1402, at Constantinople, Byzantine Emperor Manuel II Palaiologos awarded one of the Serbian magnates, Stefan Lazarević, the very high title of Despot.Although the reasons remain unknown, fifteenth- and sixteenth-century Ragusan chronicler Mavro Orbini attributes the quarrel to Lazarević's suspicions that Branković wanted to join forces with Süleyman Çelebi, Bayezid's oldest son, who held power in Rumelia.A Serbian contingent returning home from Asia Minor was abruptly attacked and destroyed near Edirne on the orders of an Ottoman commander.Branković's forces were joined by an Ottoman contingent, ordered by Süleyman to take control of local roads and prevent the Lazarević brother's crossing, which was expected to take place in the Branković-controlled territory of Kosovo.They met with their brother-in-law Đurađ II Balšić, who supported them militarily, and had their mother Milica raise an army in the Despotate.[15] Through the Gallipoli treaty in early 1403, Süleyman promised not to interfere in Serbia, on the condition that Lazarević accept his obligations towards the Ottoman Empire, which were in effect prior to the Battle of Ankara, and consisted primarily of tribute and military support.[21] In order to retain his independence from the Ottomans, who were closing in from the south, Lazarević turned to the Kingdom of Hungary, which could be counted on militarily.
There was a rift between the Lazarević brothers following the battle