Warlords in the Kanto region who obeyed Shunomaru and Anomaru, sons of late Mochiuji ASHIKAGA, who had perished in the Eikyo War, raised a rebellion against the bakufu (Japanese feudal government headed by a shogun) in 1440, establishing themselves in the Yuki-jo Castle.
永享の乱で滅びた足利持氏の遺児・春王丸と安王丸を奉じた関東の諸将が、永享12年（1440年）結城城に拠って幕府に叛旗を翻した。