Stefan Uroš V died childless in December 1371, after much of the Serbian nobility had been destroyed by the Turks in the Battle of Maritsa earlier that year. The exact cause of his death at a relatively young age remains unknown. Vukašin's son Prince Marko inherited his father's royal title, but real power in northern Serbia was held by Lazar Hrebeljanović. The latter did not assume the imperial or royal titles (associated with the Nemanjić dynasty), and in 1377 accepted King Tvrtko I of Bosnia (a maternal grandson of Stefan Dragutin) as titular king of Serbia. Serbia proper became a vassal of the Ottomans in 1390, but remained effectively ruled by the Lazarević family and then by their Branković successors until the fall of Smederevo in 1459.