He was born a son of Ashikaga Mitsukane, the third Kamakura deputy, with the childhood name Kōōmaru. The Kamakura deputy headed the Kamakura government that the Muromachi shogunate set up to rule the Kanto, a post held by descendants of Ashikaga Takauji since the first deputy, Motouji. His mother is said to have come from the Isshiki family.
His father Mitsukane died, and the young Kōōmaru succeeded as Kamakura deputy. Being still young, he relied on the Kantō kanrei to assist him in government. The next year a rumor spread that his uncle Mitsutaka was plotting rebellion, and he fled to the mansion of the Kantō kanrei Uesugi Norisada.
He came of age and, given the character "Mochi" by the shogun Ashikaga Yoshimochi in Kyoto, took the name Mochiuji. The trouble with his uncle Mitsutaka was settled by making his younger brother Otowakamaru Mitsutaka's adopted son. Bearing a name that showed his tie to the shogun, Mochiuji thus began his course as master of the Kanto.
In Ōu, Date Mochimune rebelled against Mochiuji's uncles Mitsunao and Mitsusada, who governed Mutsu as the Sasagawa and Inamura deputies. Mochiuji called on the warriors of Mutsu to gather troops and put down the revolt. As a young deputy, he showed his power to rule from the Kanto to Ōu.
Mochiuji grew cold toward the Kantō kanrei Uesugi Zenshū (Ujinori), who left the post. Resentful, Zenshū joined Mochiuji's uncle Mitsutaka and brother Mochinaka and raised troops, and Mochiuji was driven from Kamakura and fled to Suruga. This was the Uesugi Zenshū Rebellion, which split the warriors of the Kanto into two camps.
The shogunate in Kyoto decided to help Mochiuji and had Uesugi Fusakata of Echigo, Imagawa Norimasa of Suruga and others send troops. Zenshū's side was defeated; Zenshū, Mitsutaka and Mochinaka took their own lives, and Mochiuji returned to Kamakura. Even after the rebellion, however, his harsh treatment of warriors who had sided with Zenshū left embers of conflict in the Kanto.
The Kantō kanrei Uesugi Norimoto died suddenly, and his adopted son Uesugi Norizane, still a child, succeeded him. In the unusual situation of a young deputy assisted by a child kanrei, Mochiuji himself is said to have written for some time the orders that the kanrei would normally issue.
He attacked and destroyed Oguri Mitsushige of Hitachi, who was tied to the shogunate, and also defeated Utsunomiya Mochitsuna and others, seeking to rid the Kanto of warriors loyal to Kyoto. The shogun Yoshimochi considered punishing Mochiuji but called it off when Mochiuji apologized. Still, the rift between the shogunate and the Kamakura government only deepened.
When the former shogun Yoshimochi died without naming an heir, Mochiuji, as a member of the Ashikaga family, hoped to become shogun himself. But the shogunate's senior officials decided to choose by lot from among Yoshimochi's four brothers, and Yoshinori, who returned from the priesthood, became the sixth shogun. Mochiuji was deeply dissatisfied.
Mochiuji sent no envoy to congratulate Yoshinori on becoming shogun and kept using the old era name Shōchō even after it was changed to Eikyō. He also appointed abbots of Kamakura temples himself, a right that belonged to the shogun, clearly showing his refusal to obey the shogunate. The Kantō kanrei Uesugi Norizane worked to mediate between the two.
Mochiuji kept the mediating Norizane at a distance and relied on close retainers. A rumor even spread that Norizane would be killed by Mochiuji, and Norizane resigned as kanrei. Meanwhile, in Kyoto the senior officials who had restrained Yoshinori had died one after another, leaving no one to hold the shogun back.
At his heir's coming-of-age, Mochiuji broke the custom of receiving a character from the shogun and named the boy Yoshihisa. When the conflict became decisive and Norizane withdrew to Kōzuke, Mochiuji sent troops against him. Yoshinori sent a large army to aid Norizane, and Mochiuji was also branded an enemy by the imperial court. Deserted by his allies one after another, Mochiuji took Buddhist vows.
Norizane begged that the life of Mochiuji, confined at Yōanji in Kamakura, be spared, but Yoshinori refused and ordered Norizane to attack. Mochiuji took his own life at Yōanji, and his heir Yoshihisa followed him. The line of Kamakura deputies was broken for a time, but his surviving son Shigeuji later became deputy, leading on to the Koga deputies.
Ashikaga TakaujiMansaiAshikaga YoshimochiUesugi NorizaneAkamatsu MitsusukeAshikaga Yoshinori
Akamatsu MitsusukeAshikaga YoshimochiAshikaga YoshinoriIkkyū SōjunIchijō KaneyoshiYamana SōzenNisshinUesugi Norizane
People of the Muromachi period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.