Go-Shirakawa planned to regain power through the Taira's old rivals, the Minamoto. They had been steadily recovering their strength in the provinces following their defeat in 1160. In May 1180, Minamoto no Yorimasa sent a call to arms to his clan in the eastern and northern provinces. The call to arms was issued in the name of Prince Mochihito, Yorimasa's candidate for the imperial throne. Kiyomori became aware of this and subsequently confined Go-Shirakawa even more closely and called for the arrest of his son, Mochihito. Although the rebellion was defeated, it was the first of many and would eventually lead to the Taira's downfall.