Imperial Prince Sonyu also joined forces with the Aizu clan, which served as Kyoto Shugoshoku (Military Commissioner of Kyoto), and the Satsuma clan, which was on friendly terms with the Aizu clan at that time and, with the unofficial approval of Emperor Komei, staged the August 18 Deportation, which expelled from Kyoto pro-Choshu court nobles and the Choshu clan, who advocated the destruction of the Tokugawa Shogunate and the expulsion of foreign forces.
さらに尊融親王は京都守護職を務める会津藩やこの時期会津藩と友好関係にあった薩摩藩と手を結び、急進的な倒幕と攘夷決行を唱える長州派公卿と長州藩を京から排除しようとし、彼らを嫌い幕府を信頼していた孝明天皇から内意を引き出し、八月十八日の政変を行う。