The , also known as the Upheaval of Ōnin and Ōnin-Bunmei war, was a civil war that lasted from 1467 to 1477, during the Muromachi period in Japan. Ōnin refers to the Japanese era during which the war started; the war ended during the Bunmei era. A dispute between a high official, Hosokawa Katsumoto, and a regional lord, Yamana Sōzen, escalated into a nationwide civil war involving the Ashikaga shogunate and a number of in many regions of Japan.
The war initiated the Sengoku period, "the Warring States period." This period was a long, drawn-out struggle for domination by individual daimyō, resulting in a mass power-struggle between the various houses to dominate the whole of Japan.
Origin
The Ōnin conflict began as a controversy over who would succeed shōgun Ashikaga Yoshimasa. In 1464, Yoshimasa had no heir. He persuaded his younger brother, Ashikaga Yoshimi, to abandon the life of a monk, and named him heir. In 1465, the unanticipated birth of a son to Yoshimasa put these plans in question. The infant, Yoshihisa, led to a succession crisis with two competing factions. On one side was the shōgun and his brother, together with the shōgun's deputy, Hosokawa. On the other side was Yoshihisa's mother, Hino Tomiko, and her ally Yamana, who was the governor of several provinces.
Tomiko sought political and military support to rule as regent until the maturity of her son, the future shogun Ashikaga Yoshihisa. She secured the support of Yamana Sōzen and other leaders of powerful samurai clans. In contrast to Tomiko and Yamana, Yoshimi had the support of the Hosokawa clan, a powerful clan that had a great influence on the shogunate court.
The cause of the war is often attributed to the struggle to succeed the 8th shogun, Ashikaga Yoshimasa, but in fact there were multiple causes. The real power of the Ashikaga shogunate was vested in a council of powerful daimyo, but the deaths of a number of influential daimyo and the intervention in politics of women close to the shogun's entourage led to chaos in the shogunate, and from 1441 on, the masses demanded a virtue decree every few years and destroyed the sake stores and warehouses that were the source of the shogunate's funding. Under these circumstances, in addition to the conflicts over the succession of the shogun, conflicts over the succession of the Hatakeyama clan and conflicts over the succession of the Shiba clan occurred simultaneously, all of which contributed to the war. According to the most popular theory, the main cause of the war was the struggle for succession between Hatakeyama Yoshinari and Hatakeyama Masanaga within the Hatakeyama clan, with the participation of Hosokawa Katsumoto, Yamana Sōzen and other daimyo from various regions.
In 1467, these conflicts finally led to the Ōnin War between the Eastern Army, led by Hosokawa Katsumoto and including Hatakeyama Masanaga, Shiba Yoshitoshi, and Ashikaga Yoshimi, and the Western Army, led by Yamana Sōzen and including Hatakeyama Yoshinari, Shiba Yoshikado, and Ashikaga Yoshihisa.
At first, the Eastern Army supported Ashikaga Yoshimi and the Western Army supported Ashikaga Yoshihisa as the next 9th shogun. However, Ashikaga Yoshimi, who disliked war, fled to Ise to seek refuge with the Kitabatake clan, and Ashikaga Yoshimi fell out with Ashikaga Yoshimasa, the 8th shogun. When the Western Army received Ashikaga Yoshimi in 1468, the Eastern Army came to support Ashikaga Yoshihisa. In other words, the successors supported by the Eastern and Western armies reversed within a year.
Battles
thumb|left|Situation in 1467. Areas loyal to or allied with [[Hosokawa Katsumoto in pink, areas loyal to or allied with Yamana Sōzen in light green. ]]
Hosokawa's Eastern Army of about 85,000 and Yamana's Western Army of about 80,000 were almost evenly matched when mobilized near Kyoto. The fighting started in March when a Hosokawa mansion was burned. Then in May 1467, a Yamana mansion was attacked. In July, according to Sansom, Yoshimasa appointed Hosokawa commanding general in an attempt to "chastise the rebel" Yamana. Sansom states "heavy fighting continued throughout July" and "several hundred large buildings were destroyed, and destruction continued day after day". Hosokawa was soon cornered in the northeast portion of Kyoto around his mansion, while Yamana controlled the south and west. Yamana received 20,000 reinforcements under Ōuchi Masahiro in September. However, Sansom states Hosokawa was able to bring the "sovereign and the abdicated Emperor" to the Bakufu from the Emperor's Palace, before it was seized by Yamana with 50,000 men. Hosokawa then received Akamatsu troops as reinforcements. On 1 November, Yamana was able to capture the Shōkoku-ji after bribing a monk. Sansom states "The chronicles of the time paint a dreadful picture of the carnage", and "the two adversaries faced one another without action for the rest of the year". While Kyoto was burning, Ashikaga Yoshimasa spent his time in poetry readings and other cultural activities, and in planning Ginkaku-ji, a Silver Pavilion to rival Kinkaku-ji, the Golden Pavilion that his grandfather, Ashikaga Yoshimitsu, had built.
thumb|Painting depicting a battle during the Ōnin War
The Ōnin War, and the shōguns complacent attitude towards it, "sanctioned" private wars and skirmishes between the other daimyō. No part of Japan escaped the violence. Although the battles in Kyoto had been abandoned, the war had spread to the rest of Japan. In Yamashiro Province, the Hatakeyama clan had split into two parts that fought each other to a standstill. This stalemate was to have serious consequences. In 1485, the peasantry and jizamurai (lesser samurai – mostly armed peasants) had had enough, and revolted. They organized the Yamashiro ikki and forced the clan armies to leave the province. The ikki became a powerful force, much more than simply an armed mob. By 1486 they had even set up a provisional government for Yamashiro province. Mary Elizabeth Berry, and Conrad Totman argue that the kuni (provinces) were not unlike quasi-independent states, and that the term is thus more or less appropriate.
The cost for the individual daimyō was tremendous, and a century of conflict so weakened the bulk of Japanese warlords that the three great figures of Japanese unification, beginning with Oda Nobunaga, found it easier to militarily assert a single, unified military government.
Ōnin Ki
The Ōnin Ki</poem></blockquote>
</blockquote>
Chronology
The origins of the Ōnin conflict are manifold. To say that the war began with a quarrel between angry warlords is too simplistic. The initial phase of this decade-long struggle "was only a spark which set fire to a broader conflagration". Without fully anticipating the consequences, the Muromachi government had loosened the restraints of tradition in Japanese society, which meant that "new energies were released, new classes were formed, and new wealth was created". As the shogunate's powerful figures competed for influence in Kyoto, the leading families in the provinces were amassing resources and growing more independent of centralized controls.
Precursors