Ōnin War Summary

  • Last updated on November 11, 2022

A decade-long conflict fought over the right of succession to the shogunate in the Ashikaga family, this destructive struggle marked the beginning of a century in Japan known as the Sengoku Jidai, or Warring States period, a time marked by a breakdown of central authority and the dominance of local warlords.

Summary of Event

Beginning in 1338, the Ashikaga shogunate Ashikaga shogunate held nominal power over Japan. From its beginnings, however, the system of Ashikaga political control was unable to match the authority held by the previous Kamakura shoguns. Unable to control affairs away from their power base in Kyōto, successive generations of Ashikaga shoguns delegated an increasing number of responsibilities to their regional vassals, known as shugo daimyō. By the mid-fifteenth century, several of these lords had come to hold virtually autonomous control over large territories. They also had their own armies. In 1467, a succession conflict within the Ashikaga family caused two powerful shugo daimyō—Hosokawa Katsumoto and Yamana Sōzen—to go to war in support of rival claimants. This conflict, which dragged on until 1477, was named theŌnin War after theŌnin era (1467-1469) in which it began, and it is considered to be a significant turning point in the history of medieval Japan. Ōnin War[Onin War (1467-1477)] Ashikaga Yoshihisa Ashikaga Yoshimasa Ashikaga Yoshimi Hino Tomiko Hosokawa Katsumoto Yamana Sōzen Ōuchi Hosokawa Katsumoto Yamana Sōzen Ashikaga Yoshimasa Ashikaga Yoshimi Hino Tomiko Ashikaga Yoshihisa Ōuchi Hatakeyama Masanaga

In 1464, Ashikaga Yoshimasa, the eighth Ashikaga ruler, made known his wish to retire from his position as shogun because of his dissatisfaction with the stresses of public life. This practice was not uncommon in Japanese history and Yoshimasa was not considered to be a strong leader, but his intention to retire nevertheless sent ripples of discontent through the shogunal court. Lacking a male heir, Yoshimasa decided to name his brother Yoshimi as his successor. Yoshimi, who had earlier chosen to become a Buddhist monk because high political office was not open to him, was persuaded to quit the priesthood to take up the office of shogun.

Shortly thereafter, however, Yoshimasa’s wife, Hino Tomiko, bore him a son who was named Yoshihisa. It was first believed that this would settle the succession issue, but despite the fact that his brother now had a legitimate heir, Yoshimi did not wish to surrender his claim to the office, and Hino, a strong-minded woman experienced in the machinations of life at the shogunal court, decided that she would stop at nothing to see her son named as heir. The situation quickly degenerated when both parties sought outside assistance. Hosokawa Katsumoto, a major political figure and the leader of the powerful Hosokawa family, chose to support Yoshimi, while Yamana Sōzen, a powerful landholder in the west who had built up his power base through ruthless military raiding, backed Hino and her son. Both sides began to move troops, first into the environs of Kyōto and then into the capital itself. War began in earnest in 1467 when a skirmish broke out between the two sides.

TheŌnin War was characterized more by destructive street fighting in and around Kyōto than decisive battles. The result was a costly war of attrition for the rival blocs. From the beginning of the fighting, both the Hosokawa and the Yamana dragged allies into the conflict, worsening the stalemate. Contemporary accounts estimate that each side had approximately eighty thousand men at the beginning of the conflict. Yamana relied heavily on allied forces, so it was believed that Hosokawa, whose troops were thought to be more loyal, had a slight advantage. Nevertheless, numbers were not a decisive factor in the fighting, as neither side could outmaneuver the other. Arson became an important tactic on the urban battlefield, and a large part of the city was razed to the ground as the conflict proceeded. In addition, both sides began to build barricades in the streets, and networks of trenches were dug near the outskirts of the city. There are also reports in contemporary chronicles of improvised catapults being employed in an attempt to introduce a decisive edge to the action. As the war progressed and more areas of the city were reduced to ruins, large-scale military action became possible, but no tactics emerged to break the stalemate.

As the war dragged on, all parties began to become restless. As a result of his role in the fighting, Ashikaga Yoshimi, who had originally held the support of his brother, alienated the shogun, who then chose to support his son, Yoshihisa, as heir in 1469. This proved to be a momentary advantage for Yamana and his men. However, in 1473 both Hosokawa Katsumoto and Yamana Sōzen died of illness. The succession issue, nominally the cause of the conflict in the first place, was also settled in that year, and Yoshihisa became shogun in 1474. By this time, however, the allies of Hosokawa and Yamana were intent on working out their territorial rivalries and sporadic fighting continued.Ōuchi, a powerful Western daimyo (local warlord) Daimyos who had entered the conflict on the side of the Yamana with twenty thousand men in 1467, chose to pursue a personal vendetta against the daimyō Hatakeyama Masanaga in 1475, and fierce fighting took place in Kyōto and in regions south of the city. In late 1477,Ōuchi complied with a request from the shogun to withdraw his forces from Kyōto, and after a decade that has come to be regarded as one of the most fruitless and destructive in Japanese history, theŌnin War finally came to a close.


TheŌnin War was an important turning point in the history of medieval Japan. When the fighting ended in 1477, the ancient capital Kyōto had been devastated and the military government of the Ashikaga shogunate was in shambles. The Ashikaga shoguns were never able to regain the measure of authority that they had exercised before the beginning of the conflict, and the power of the shugo daimyō houses that owed them allegiance also began a swift decline. The undermining of central authority that theŌnin War represents opened the way for ambitious regional barons known as sengoku daimyō to gain power over small areas of the country. These local strongmen fought against one another, and their conflicts ushered in a century-long period of civil strife known as the Sengoku Jidai or Warring States period Warring States period (Japan, 1477-1600) .

While theŌnin War did immeasurable damage to Kyōto and its cultural legacies, the political situation that it created brought about many positive developments. Local rulers, in an attempt to consolidate their authority, improved infrastructure and made efforts to increase agricultural production. In addition, they supported craftspeople and the fine arts. The result was cultural and material advancement that culminated in the late sixteenth century when a series of three military leaders—Oda Nobunaga, Toyotomi Hideyoshi, and Tokugawa Ieyasu—known as the Three Unifiers—brought the Warring States period to an end by once again consolidating central power.

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Sansom, George. A History of Japan, 1334-1615. 3 vols. Stanford, Calif.: Stanford University Press, 1961. Despite its age, Sansom’s history of premodern Japan is still the most authoritative on the subject in English. Includes a detailed chapter on the Ōnin War.
  • citation-type="booksimple"

    xlink:type="simple">Sato, Hiroaki. Legends of the Samurai. New York: The Overlook Press, 1995. One of the best collections of writing about the wars and culture of the samurai in English.
  • citation-type="booksimple"

    xlink:type="simple">Turnbull, Stephen. The Samurai Sourcebook. London: Arms and Armour Press, 1998. Offers encyclopedic coverage of the important figures in the history of the samurai as well as aspects of their military culture.
  • citation-type="booksimple"

    xlink:type="simple">Varley, H. Paul. The Onin War. New York: Columbia University Press, 1966. The authoritative account of the conflict in English. It contains not only a history of the war itself but also translations from surviving accounts of the fighting and political dealings that surrounded it.

1457-1480’s: Spread of Jōdo Shinshū Buddhism

1477-1600: Japan’s “Age of the Country at War”

Mar. 5, 1488: Composition of the Renga Masterpiece Minase sangin hyakuin

Beginning 1513: Kanō School Flourishes

1532-1536: Temmon Hokke Rebellion

1549-1552: Father Xavier Introduces Christianity to Japan

1550’s-1567: Japanese Pirates Pillage the Chinese Coast

1550-1593: Japanese Wars of Unification

Sept., 1553: First Battle of Kawanakajima

June 12, 1560: Battle of Okehazama

1568: Oda Nobunaga Seizes Kyōto

1587: Toyotomi Hideyoshi Hosts a Ten-Day Tea Ceremony

1590: Odawara Campaign

1592-1599: Japan Invades Korea

1594-1595: Taikō Kenchi Survey

Oct., 1596-Feb., 1597: San Felipe Incident

Oct. 21, 1600: Battle of Sekigahara

Categories: History