Eiroku Incident (Japanese: 永禄の変) was an event on 19 May of Eiroku 8 (17 June 1565), when Miyoshi Sannin-shū (三好三人衆)1 and Matsunaga Hisahide led their troops in an attack on the Nijō Gosho (二条御所) in Kyoto, where the 13th Shogun of the Muromachi shogunate, Ashikaga Yoshiteru, was residing, and assassinated Shogun Yoshiteru.
Background
Rise of the Miyoshi clan
The Shugodai of Awa, the Miyoshi clan (三好氏), wandered across the Kinai region due to internal strife within the Hosokawa clan (細川氏) over the post of Kanrei. Miyoshi Motonaga (三好元長) was the greatest contributor to making Hosokawa Harumoto (細川晴元) Kanrei, but this became the source of his downfall; Harumoto, fearing his power, came to regard Motonaga as a danger, and in the end Motonaga was attacked by the forces of Honganji from Izumi Province in the Battle of Iimori Castle (飯盛城の戦い) and committed suicide.2
Motonaga's son, Miyoshi Nagayoshi, steadily expanded his power while opposing the Ashikaga shogun and Kanrei Harumoto. Thus, in Tenbun 22 (1553), he expelled Shogun Ashikaga Yoshiteru to Kutsuki in Ōmi Province, and the Miyoshi clan stood at the apex of central power as the leading force in the Kinai region.
However, during the Sengoku period, it was difficult to rule Kyoto while opposing the shogun and without relying on the structure of shogunal government. Moreover, even after Yoshiteru moved to Kutsuki in Ōmi, the Rokkaku clan of Ōmi and the Hatakeyama clan of Ise continually attacked, so the Miyoshi clan's rule over Kyoto never stabilized. Therefore, in the first year of Eiroku (1558), Nagayoshi, attacked by Rokkaku Yoshikata (六角義賢) of Ōmi, reconciled with Shogun Yoshiteru, and was admitted into the ranks of the Goshōhanshū (御相伴衆) of the shogunate.
Thus, although the Miyoshi clan firmly controlled Kyoto, in form it had entered the shogunate's political apparatus as a vassal of Shogun Yoshiteru.
Decline of the Miyoshi clan and restoration of shogunal authority
Furthermore, from around this time, influential members of the clan, including Sogō Kazumasa (十河一存) and Miyoshi Yoshikata (三好義賢), both younger brothers, and Miyoshi Yoshioki (三好義興), Nagayoshi's eldest son, died one after another. Eventually, Nagayoshi himself had his younger brother Atago Fuyuyasu (安宅冬康), who had supported him until the end, assassinated after believing slander, and the power of the Miyoshi clan began to decline rapidly. Finally, in Eiroku 7 (1564), Nagayoshi himself died, and a deeper shade of ruin fell over the Miyoshi clan.
Meanwhile, Shogun Yoshiteru pursued the restoration of shogunal authority through vigorous activities, such as mediating conflicts between Sengoku daimyo across the country and granting Yakushoku (役職). Furthermore, using the Miyoshi clan, in Eiroku 7 (1564) he drove Ise Sadataka (伊勢貞孝), who had opposed him and was the Mandokoro shitsuji (政所執事)3, to death, and appointed Settsu Harukado (摂津晴門), a cousin of Yoshiteru, as the new Mandokoro shitsuji, thereby seizing control of the Mandokoro, which had not moved according to the shogun's wishes, strengthening his influence over shogunal decisions, and steadily establishing a system of direct shogunal rule within the shogunate as the most intelligent shogun since Ashikaga Yoshimitsu (足利義満).
Because of this situation, the Miyoshi clan came to feel a sense of crisis regarding Shogun Yoshiteru. Thereupon, Matsunaga Hisahide and the Miyoshi Sannin-shū, who had seized actual power within the Miyoshi clan in place of Nagayoshi's heir, Miyoshi Yoshitsugu (三好義継), came to plan Yoshiteru's exclusion, that is, his assassination.
Eiroku Incident
Matsunaga Hisahide and the Miyoshi Sannin-shū schemed to depose Shogun Yoshiteru and enthrone Yoshiteru's cousin Ashikaga Yoshihide (足利義栄) as shogun. At about 8 a.m. on 19 May of Eiroku 8 (1565), they led their armies and attacked and surrounded the Nijō Gosho where Yoshiteru was staying. Yoshiteru's side had made preparations against the Miyoshi attack, such as rebuilding the defenses of the palace, but being greatly outnumbered, they could not prevail. The shogun's attendants fought bravely against the Miyoshi forces despite their small numbers, but around noon Yoshiteru was killed in action, and his birth mother Keishu-in (慶寿院, daughter of Kampaku Konoe Hisamichi (近衛尚通) and principal wife of the 12th shogun Ashikaga Yoshiharu (足利義晴)) also died by suicide. It is said that Yoshiteru, who had been taught by the swordsman Tsukahara Bokuden (塚原卜伝), was skilled with the sword, and at this time he personally took up a blade and fought, cutting down enemies with a fearsome momentum.
Because of this assassination of the shogun, the authority of the shogunate fell markedly once again.
After the Eiroku Incident
Immediately after Yoshiteru's assassination, Matsunaga Hisahide and his associates confined Kakukei (覚慶, later Ashikaga Yoshiaki (足利義昭)), Yoshiteru's younger brother who was a monk at Kōfuku-ji in Nara. However, two months later, on 28 July, Kakukei escaped with the help of Yoshiteru's close attendants Isshiki Fujinaga (一色藤長) and Hosokawa Fujitaka (細川藤孝), among others. Kakukei returned to lay life in February of the following year, taking the name Ashikaga Yoshiaki (足利義秋), and placed himself under the protection of Asakura Yoshikage (朝倉義景), the Shugo of Echizen.
Meanwhile, the Miyoshi Sannin-shū enthroned Ashikaga Yoshichika (足利義親, later renamed Ashikaga Yoshihide (後に義栄)), a cousin of Yoshiteru of the Sakai kubō lineage, as shogun in Awaji Province.
Yoshiteru and Nagayoshi
When considering this incident, and further the strengthening of Ashikaga Yoshiteru's shogunal power, the problematic point is the distance between Yoshiteru and the Miyoshi clan. As the earlier-mentioned subjugation of Ise Sadataka symbolizes, the restoration of shogunal power by Yoshiteru, who lacked his own military force (especially the restoration of power as a ruler of the Kinai backed by military force, beyond the authority as a mediator among daimyo, which could be exercised with letters and envoys alone), was in fact possible only because Miyoshi Nagayoshi took a conciliatory stance toward the shogunate.
Nagayoshi pursued his own interests strongly, yet consistently maintained an attitude of respect toward the shogun's house. However, even in this period Yoshiteru made several attempts to assassinate Nagayoshi, which strongly suggests that he never considered that such attempts would, far from strengthening his power base, instead bring about its collapse. It can be seen that the exclusion of Shogun Yoshiteru was originally not an idea of Miyoshi Sannin-shū or Matsunaga Hisahide, but was first devised by Hosokawa Mochitaka (細川持隆), the Shugo of Awa Province, and that Yoshiteru, who insisted on absolute shogunal rule from the start, was a troublesome figure to many shogunate officials.
Footnotes