In 1156, after the death of the Cloistered Emperor Toba, the Retired Emperor Sutoku and Emperor Goshirakawa, who had fallen into conflict over the imperial succession, reached the point where it was no longer possible to avoid armed conflict, and so each camp began recruiting powerful warriors.
翌保元元年（1156年）、鳥羽法皇の死後、皇位を巡って対立していた崇徳上皇と後白河天皇の武力衝突が不可避の情勢になり、双方の陣営が有力な武士を招聘していた。