The Eisho Disturbance — The Great Upheaval of Kanto and Echigo and the Turn to the Sengoku Age

The Eishō Disturbance (Eishō no Ran) was a complex power struggle that unfolded in the Kantō, Echigo, and Hokuriku regions from Eishō 3 (1506) to Eishō 17 (1520). It consisted of a series of conflicts: the civil war in Echigo, the internal dispute of the Yamanouchi Uesugi clan, the internal dispute of the Koga kubō household, and the subjugation of the Jinbō clan in Etchū. The death in battle of Kantō kanrei Uesugi Akisada in the civil war in Echigo, which began with the rebellion of the Echigo shugodai (deputy governor) Nagao Tamekage, triggered the strife in Kantō. Through this disturbance, the authority of the Muromachi shogunate declined rapidly, and the rise of daimyo power accelerated. It is an important incident that marks the transition to the Sengoku period.

Background: The Decline of the Muromachi Shogunate and the Destabilization of Kantō

From the late 15th to the early 16th century, Japan as a whole was in political turmoil. In the capital, the power of the shogun was gradually waning, and daimyo across the country were growing more independent. In Kantō, since the Kyōtoku War, the Koga kubō (a branch of the Ashikaga family) and the Kantō kanrei (of the Uesugi clan) had remained in conflict. However, in the time of Ashikaga Masauji, the 2nd Koga kubō, a cooperative arrangement with Kantō kanrei Uesugi Akisada had been adopted.

In the Koga kubō household, Ashikaga Masauji had become the 2nd kubō in Entoku 1 (1489) after receiving the headship from the first kubō, Ashikaga Shigeuji. In Eishō 3 (1506), however, the conflict between Masauji and his eldest son, Takauji (later Ashikaga Takamoto), came to the surface. Meanwhile, Uesugi Akisada, who held the post of Kantō kanrei as head of the Yamanouchi Uesugi clan, had reconciled in Eishō 2 (1505) with the Ōgigayatsu Uesugi clan, with whom he had fought in the Chōkyō War. He had also taken Masauji's younger brother, Akizane, as his adopted son.

In Echigo Province, the Nagao clan served as shugodai under the shugo, Uesugi Fusayoshi, Akisada's biological younger brother. In the 9th month of Eishō 3 (1506), shugodai Nagao Yoshikage died in battle in Etchū, and his son Nagao Tamekage succeeded to the headship of the family and the post of shugodai. In the 8th month of Eishō 4 (1507), Tamekage backed Uesugi Sadazane and launched a sudden attack on Fusayoshi. When Fusayoshi tried to flee toward Kantō, Tamekage drove him to commit suicide at Amamizukoshi.

Course of the War: The Civil War in Echigo and the Internal Strife in Kantō

In Eishō 6 (1509), Kantō kanrei Uesugi Akisada led a large army into Echigo to avenge his younger brother Fusayoshi. Tamekage, who had fallen into a disadvantageous position, fled to Sado (also given as Etchū).

In the following year, Eishō 7 (1510), however, Tamekage landed again in Echigo from Teradomari and turned to counterattack. Akisada failed to win the support of Echigo's local lords (kokujin) and tried to withdraw to Kantō. On the 20th day of the 6th month of Eishō 7 (1510), he was attacked at Nagamorihara (present-day Minamiuonuma, Niigata Prefecture) by Tamekage and the reinforcements of Takanashi Masamori, and was killed in action (Battle of Nagamorihara). The death of the head of the Uesugi clan on the battlefield symbolized the rapid decline of the authority of the Kantō kanrei.

After Akisada's death, his adopted son Akizane and Norifusa contested the headship of the Yamanouchi Uesugi clan. Akizane gained the support of his biological elder brother, the Koga kubō Ashikaga Masauji, while Norifusa gained the support of Masauji's eldest son, Takamoto, and Kantō was split in two. Takamoto became the 3rd Koga kubō in Eishō 9 (1512). When Masauji took vows and retired to his residence at Kuki in Musashi Province in Eishō 15 (1518), the internal strife of the Koga kubō household subsided. In Echigo, Tamekage took real power by placing Uesugi Sadazane in the position of shugo. Together with the Noto shugo, Hatakeyama Yoshifusa, he then attacked and destroyed Jinbō Yoshimune of Etchū, who had driven Tamekage's father, Yoshikage, to his death.

Historical Significance: A Turning Point Toward the Sengoku Period

The greatest historical significance of the Eishō Disturbance lies in the fact that it symbolizes the rapid collapse of the authority of the Muromachi shogunate in this period and the beginning of the rise of daimyo power. The Kantō kanrei was originally a key post for governing Kantō by assisting the Kamakura kubō (later the Koga kubō), but through the Eishō Disturbance, the military power of the Yamanouchi Uesugi clan was greatly diminished. In its place, in Echigo, the shugodai Nagao Tamekage took real power over the province by supporting the shugo, Uesugi Sadazane.

After this war, the power structure of Kantō changed completely. The power of the Koga kubō declined rapidly. Ise Sōzui (Hōjō Sōun) and his successors (the Later Hōjō clan), who had already advanced into Sagami during the course of the war, eventually came to dominate Kantō. The background to the full-scale advance of the Hōjō clan into Kantō was that the authority of the Koga kubō and the Uesugi clan had fallen because of the Eishō Disturbance, leaving a vacuum.

The Eishō Disturbance may appear to be merely a local dispute over the succession to power. Through this war, however, the path opened in Kantō and Echigo toward sengoku daimyo who governed their domains by their own strength. Samurai bearing swords and spears no longer simply obeyed the authority of the shogunate. Instead, they began to act as sengoku daimyo who acquired and maintained their own territories by their own military power. In that sense, the Eishō Disturbance is a symbolic incident that reflects the qualitative change in warrior society.