The reason given was that Yorishige had been plotting to usurp the position of Shogun himself, but given the poor relations with the shogunate, for the retired Emperor Gotoba to send the court's military forces into action for such a reason would have been unnatural, and so it is thought that Gotoba struck because Yorishige had learned Gotoba had been carrying out incantations and prayers to curse Kamakura.
理由は頼茂が将軍に就こうと図ったためとされているが、幕府の問題のために後鳥羽上皇が朝廷の兵力を動かすのは不自然であり、頼茂が後鳥羽上皇による鎌倉調伏の加持祈祷を行っていた動きを知ったためと考えられている。