According to the "Heike monogatari," the motive for the uprising was that Yorimasa's son and heir Nakatsuna had become embroiled in discord with TAIRA no Munemori (Kiyomori's third son) over a horse.
『平家物語』では、挙兵の動機は、頼政の嫡男・仲綱と平宗盛（清盛の三男）の馬をめぐる軋轢ということになっている。