In 1221, opposition deeper between the Retired Emperor Gotoba, wishing to re-capture authority for the Imperial Court, and the government, and finally the Emperor attacked Mitsusue IGA, the Shugo (military governor) in Kyoto and established a military police force.
承久3年（1221年）皇権の回復を望む後鳥羽上皇と幕府との対立は深まり、遂に上皇は京都守護伊賀光季を攻め殺して挙兵に踏み切った。