 Lazar briefly participated in the war as one of the opponents of Prince Sigismund of Luxemburg, and he sent some troops to fight in the regions of Belgrade and Syrmia.These fights ended with no territorial gains for Lazar, who made peace with Sigismund in 1387.In the Battle of Kosovo fought on 15 June 1389, Lazar led the army which confronted a massive invading army of the Ottoman Empire commanded by Sultan Murad I.