title "emperor of Serbs and Greeks". There is one account, early in his reign, that is in contrast to his general record of incompetence. In 1356, Matthew Kantakouzenos, a pretender to the Byzantine throne, gathered an army of 5,000 Turks and marched on Serres, the Serbian-held capital of Jovan Uglješa. Uroš V, whose mother ruled from Serres, decided to raise an army to defend his mother. In 1357, when Matthew and his Turks attacked, the Serbian army under Vojihna of Drama (a major player in that region) came to aid. The Turks were defeated. Matthew Kantakouzenos was captured and held hostage until his ransom was paid by the Byzantine Emperor John V Palaiologos. In following years, the Serbian Empire gradually fragmented into a conglomeration of principalities, some of which did not even nominally acknowledge Uroš's rule. His position was not helped by his mother Helena, who started to rule autonomously from Serres in alliance with Jovan Uglješa. A similarly autonomous posture was assumed by the Dejanović family, the Balšić family, Nikola Altomanović. By 1365, the most powerful Serbian nobleman became Uglješa's brother Vukašin Mrnjavčević who became co-ruler with Emperor Uroš and was granted the title of Serbian King. By 1369, as Uroš was childless, Vukašin designated his eldest son Prince Marko as heir to the throne, with the title of "young king". 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. Following the great conquests of his father, Uroš became a victim of new nobles in a Serbia enriched by recent war and pillaging. The maintaining of order and state instruments was impossible because of weak or nonexistent infrastructure between the old and new territories. The exceptional modesty and tolerance of this