Mochiuji became Kubō while still a child after his father died suddenly of a disease. His violent and abrasive character from the beginning caused widespread resentment among his vassals. After disagreements with Mochiuji, his kanrei Uesugi Zenshū organized a rebellion against him (the so-called Zenshū no Ran) with the aid of nearly half the daimyos in the northern and eastern provinces. Thanks to this support, Zenshū could take Kamakura and Mochiuji had to flee. However, despite his pursuing goals similar to those of the shogunate, Zenshū was after all rebelling against his lord, so the shogunate had no choice but to send troops to stop him. In 1417, Zenshū and his allies found themselves surrounded at Tsurugaoka Hachiman-gū and Zenshū killed himself.