Lazar and Tvrtko I, the Ban of Bosnia, jointly defeated in 1373 another strong noble, Nikola Altomanović. Most of Altomanović's territory was acquired by Lazar. About that time, Lazar accepted the suzerainty of King Louis I of Hungary, who granted him the region of Mačva, or at least a part of it. With all these territorial gains, Lazar emerged as the most powerful Serbian lord. The state he then created is known in historiography as the Principality of "Moravian Serbia".