polities, and to independence from Hungarian rule. Wallachia's creation, held by local traditions to have been the work of one Radu Negru (Black Radu), is historically connected with Basarab I of Wallachia (1310–1352), who rebelled against Charles I of Hungary and took up rule on either side of the Olt, establishing his residence in Câmpulung as the first ruler of the House of Basarab. Basarab refused to grant Hungary the lands of Făgăraș, Almaș and the Banate of Severin, defeated Charles in the Battle of Posada (1330), and, according to Romanian historian Ștefan Ștefănescu, extended his lands to the east, to comprise lands as far as Kiliya in the Budjak (reportedly providing the origin of Bessarabia); the supposed rule over the latter was not preserved by the princes that followed, as Kilia was under the rule of the Nogais c.1334. There is evidence that the Second Bulgarian Empire ruled at least nominally the Wallachian lands up to the Rucăr–Bran corridor as late as the late 14th century. In a charter by Radu I, the Wallachian voivode requests that tsar Ivan Alexander of Bulgaria order his customs officers at Rucăr and the Dâmboviţa River bridge to collect tax following the law. The presence of Bulgarian customs officers at the Carpathians indicates a Bulgarian suzerainty over those lands, though Radu's imperative tone hints at a strong and increasing Wallachian autonomy. Under Radu I and his successor Dan I, the realms in Transylvania and Severin continued to be disputed with Hungary. Basarab was succeeded by Nicholas Alexander, followed by Vladislav I. Vladislav attacked Transylvania after Louis I occupied lands south of the Danube, conceded to recognize him as overlord in 1368, but rebelled again in the same year; his rule also witnessed the first confrontation between Wallachia and the Ottoman Empire (a battle in which Vladislav was allied with Ivan Shishman). 1400–1600 Mircea the Elder to Radu the Great As the entire Balkans became an integral part of the growing Ottoman Empire (a process that concluded with the fall of Constantinople to Sultan Mehmed the Conqueror in 1453), Wallachia became engaged in frequent confrontations in the final years of the reign of Mircea I (r. 1386–1418). Mircea initially defeated the Ottomans in several battles, including the Battle of Rovine in 1394, driving them away from Dobruja and briefly extending his rule to the Danube Delta, Dobruja and Silistra (c. 1400–1404). He swung between