Lazar left the court Tsar Uroš in 1363 or 1365, and became a regional lord. He held the title of prince since at least 1371. His territory initially developed in the shadow of stronger regional lords. The strongest were the Mrnjavčević brothers, Vukašin and Jovan Uglješa. They were defeated and killed by the Ottoman Turks in the Battle of Maritsa in 1371, after which Lazar took a part of their territory.