According to the "Heike Monogatari," Yorimasa decided to stand against Kiyomori because TAIRA no Munemori, third son of Kiyomori, severely insulted Yorimasa on a matter related to a horse of Nakatsuna; Yorimasa decided to raise an army against the Taira clan out of the pride of samurai and visited Prince Mochihito's residence during the night to encourage him to stand up against Kiyomori.
挙兵の動機について、『平家物語』では仲綱の馬を巡って清盛の三男の平宗盛がひどい侮辱を与えたことが原因であるとし、頼政は武士の意地から挙兵を決意して夜半に以仁王の邸を訪ね、挙兵をもちかけたことになっている。