As his father Taira no Kiyomori lay on his deathbed, Kiyomori declared, among his last wishes, that all affairs of the clan be placed in Munemori's hands. His favorite, and eldest, son, Shigemori, had died, and so Munemori was next in line. In 1183, as the rival Minamoto clan gained power, and following the defection of Emperor Go-Shirakawa to the Minamoto side, Munemori led his forces, along with the young Emperor Antoku west, to the Taira strongholds of Shikoku and Kyūshū. By the end of the year, they'd set up a temporary Imperial Court at Yashima.