Toghon Temür, the last Yüan emperor of China and a Genghisid of the Toluy-Qubilay line, fled in 1368 to Mongolia after the dynasty's defeat and replacement by the national Ming Dynasty. From then on, his descendants and those of other Genghisid lineages would claim the right to rule the Mongols, but without achieving the re-establishment of even a unified Mongolia, to say nothing of a resurrection of the Genghisid empire. The challenge of reconquering the northern and western portions of Mongolia itself, with the historic region of Qaraqorum, from their linguistic cousins the Oirats proved an arduous and protracted task. The able and energetic Dayan Khan (enthroned in 1470, ruled from 1481) failed to do so despite the campaigns he waged from 1492 on, and success was granted only to his equally remarkable grandson Altan Khan (1543–83) and the latter's great-nephew Khutukhtai Sechen Khungtaiji, chief of the Ordos tribes (1540–86). Their victory over the Oirats in 1552 was to benefit especially the Khalkha component of the Eastern Mongols, who occupied these central and northwestern segments of the country that eventually became the core of modern Mongolia. For the time being, however, the center of political power among Eastern Mongols was in territories corresponding to what is now Inner Mongolia, more specifically areas inhabited by the tribes of Tüet and Ordos.