The Eishō Discord (Eishō no naikō) occurred in Eishō 3 (1506). This involved an internal conflict in the Shimotsuke-Utsunomiya clan based on a disagreement between Utsunomiya Shigetsuna (the seventeenth head of the Shimotsuke-Utsunomiya clan) and his chief retainer, Haga Takakatsu, in regard to governing policies. This event gave rise to the Utsunomiya Disturbance, an outbreak of hostilities between members of the Shimotsuke-Utsunomiya clan that ran from 1512 to 1514.
Utsunomiya Shigetsuna and the Haga clan
From the latter part of the Muromachi period, the Utsunomiya clan experienced leadership successions with when the heads were still very young. This occurred with Utsunomiya Akitsuna (the fifteenth head assumed the role at age eighteen and died at twenty-one) and Utsunomiya Masatsuna (the sixteenth head assumed the role at age sixteen and died at thirty). Amidst this lack of experience among successive heads, retainers led by the Haga and Mumo clans gained significant influence.
In 1477, Masatsuna died of illness and was succeeded by his eldest son, Utsunomiya Shigetsuna, at the age of nine. This succession was said to have triggered a dispute with the Mumo clan. The Mumo had a scheme by which Mumo Rokurō would become the next head of the Utsunomiya clan, whereas Haga Takamasu and Haga Kagetaka supported Shigetsuna as the successor, thwarting the wishes of the Mumo. Later, the Mumo rebelled, but Takamasu, Kagetaka, and Shigetsuna obtained recognition from Ashikaga Shigeuji, the Koga kubō and suppressed the Mumo. This incident severely undermined the authority of the Mumo so that the Haga clan continued to rise on its own. Perhaps owing to these circumstances, the Haga clan steadily increased its power to almost be on a par with Shigetsuna in his role as head of the Utsunomiya clan.
Internal conflict within the family of the Koga kubō
During the early part of the Sengoku period, provinces in the eastern region were highly unstable. The break out of fighting across the region during this time is known as the Eishō Conflict (Eishō no ran).
The conflict gradually spread to northern Kantō. In 1506, a political dispute arose between Ashikaga Masauji (the Koga kubō) and his designated heir, Ashikaga Takamoto. Owing to this confrontation, Takamoto fled to the Shimotsuke-Utsunomiya for protection from his father-in-law, Shigetsuna. This gave Shigetsuna a reason to intervene in the internal dispute besetting the family of the Koga kubō. Shigetsuna backed Takamoto as the next Koga kubō and aimed to expand his influence.
Confrontation with Haga Takakatsu
During the Meiō era (1492-1501), Haga Kagetaka transferred control of the clan to his heir, Haga Takakatsu, and retired. Takakatsu displayed arrogant conduct that caused friction with Shigetsuna. In 1506, schemed for his son-in-law, Ashikaga Takamoto, to become the Koga kubō, but Takakatsu supported Ashikaga Masauji, the Koga kubō at the time. Takakatsu then joined wit the Oyama clan and others in opposition to Shigetsuna.
In 1511, the relations between Shigetsuna and Takakatsu further deteriorated, escalating into armed conflict. Through the artifice of Takakatsu, Shigetsuna’s heir, Utsunomiya Tadatsuna, received backing while Shigetsuna was forced to retire. Afterwards, however, Shigetsuna continued to be the de facto head of the clan, and retained his authority. Moreover, during this period, Shigetsuna sent his younger brother, Takatsuna, to the Shionoya clan to become their next leader, while another younger brother, Kanetsuna, became the next head of the Mumo clan. The circumstances of Shigetsuna’s retirement and the backing of Tadatsuna by Takakatsu was behind Shigetsuna’s plan to garner complete control of the family,
In the fourth month of 1512, Shigetsuna murdered Takakatsu, who until such time had been gaining influence. This killing escalated into a broad internal conflict that triggered a major revolt by the Haga clan known as the Utsunomiya Disturbance. The rising influence of the Haga clan was comparable to the Utsunomiya. After two years of conflict, and with the support of Ashikaga Takamoto (his son-in-law) and Yūki Masatomo (his younger brother-in-law), along with the contributions of Mibu Tsunashige, Shigetsuna suppressed the revolt. As a result, the Haga clan was incorporated into a governance structure with Shigetsuna at the top, while he succeeded in threatening Ashikaga Masauji (the Koga kubō who had fled to Oyama in Shimotsuke) from behind the scenes.