Japan Castle Explorer: Onishi Castle -Prototype of pre-modern regime (1) down the river and across the straight-

Onishi Castle

-Prototype of pre-modern regime (1) down the river and across the straight-

Overview

Name: Onishi castle (Onishi-jo)
Alias: Ikeda-jo (Ikeda castle)
Place: Ikeda-cho Miyoshi city, Tokushima
Type: Hill Castle
Built: 13th century
Remaining remnants: Stone walls
Title:

Brief History

Onishi castle (大西城) is built over a long and narrow peninsula like height of 50 meter height between crescent shaped curved Yoshino-gawa river and backside mountains in the center of current Miyoshi city. This area consist of above height appropriate for the castle or residence of the lord, rectangular flat terrace of about 1,000 meter long and 500 meter wide at the south of plateau totally protected by mountains, plateaus and forefront creeks, and riverbed area of Yoshino-gawa river which used as a river port, and an ideal place to build castle and castle town.

In addition to this shape, geographically this place was a center of communication of Shikoku island. Yoshino-gawa river, the largest river of Shikoku island, starts from mountainous area in the north of current Kochi prefecture flows toward east at first then turned to the north and crosses Shikoku mountains, then turned to east again at the place of Onishi castle and runs straightly toward east to the mouth at current Tokushima city area.

From this point Tosa province (Kochi prefecture) and Iyo province (Ehime prefecture) is accessible tracing Yoshino-gawa river and its tributary Dozan-gawa respectively, and by crossing short mountainous route it is connected to coastal area of Iyo province or Sanuki province (Kagawa prefecture). At a glance it seems a quiet mountainous town, but it had been a center of communication and logistics of Shikoku island.

Origin of Ikeda castle and Miyoshi clan

Precise year is unknown but Onishi castle is built in the former half of 13th century by Ogasawara clan. Ogasawara clan was originally a local lord of Kai province (Yamanashi prefecture). Ogasawara clan activated at the establishment of Kamakura Shogunate by Yoritomo Minamoto (1147-1199) and gained Shinano province (Nagano prefecture), and well fought at the battle of Jokyu occurred in 1221, and also seized Awa province.

Ogasawara clan placed their descendants over the province, and the house lived at Onishi castle later changed their surname to Miyoshi clan, using the name of providence. In the former half of Muromachi era Miyoshi clan belonged to the South Court and resisted against Hosokawa clan which was appointed as the governor of Awa province by Muromachi Shogunate, but later followed to Hosokawa clan and became its retainer.

Miyoshi clan gradually grew up to the important retainer of Hosokawa clan, being supported by wealth from the trade of wood and indigo produced at mountainous area by Yoshino-gawa river, and strong soldiers grew in the hard life of area. Later Miyoshi clan went down the river and moved to Shozui castle, the main base of Hosokawa clan, and left Onishi castle to Onishi clan which was the lord of Hakuchi castle close to Onishi castle.

Seizure of Muromachi Shogunate by Hosokawa clan

Hosokawa clan to which Miyoshi clan served was a relative of Muromachi Shogunate and one of the three houses which had the qualification to be appointed as "Kanrei", the general governor of Muromachi Shogunate. Shiba clan at the same position already declined, and Hatakeyema clan also suffered internal conflict for successor.

In 1467, because of the internal conflict for successor of both of Muromachi Shogunate itself and Hatakeyema clan, the battle of Onin started at Kyoto city. The battle intermittently continued over 11 year at the capital Kyoto city, and the authority of Muromachi Shogunate significantly declined. Hosokawa clan became the leader of the East Army, and virtually won the battle then became the prominent power of Shogunate.

In 1493, Masamoto Hosokawa (1466-1507), the leader of Hosokawa clan, expelled 10th Shogun Yoshitane Ashikaga (1466-1523) from Kyoto city, and placed Yoshizumi Ashikaga (1481-1511) as 11th Shogun. It was the first time that the Shogun was replaced by its retainer, and Muromachi Shogunate virtually became the government of Hosokawa clan.

Disorder of Hosokawa clan

However, as Masamoto Hosokawa did not marry and had no son, Masamoto adopted three sons Sumiyuki Hosokawa (1489-1507), Sumimoto Hosokawa (1489-1520) and Takakuni Hosokawa (1484-1531) as candidates of successor. Naturally there arouse internal conflict for successor after the death of Masamoto, and at first the battle between Sumiyuki, and ally of Sumimoto and Takakuni occurred in 1507.

As Sumimoto Hosokawa was a person of Awa house of Hosokawa clan, Yukinaga Miyoshi (1458-1520), the leader of Miyoshi clan, crossed Akashi straight and landed to Kyoto city to serve to Sumimoto. At this time Sumimoto Hosokawa ruined Sumiyuki Hosokawa and succeeded Hosokawa clan, and Motonaga Miyoshi supported Sumimoto Hosokawa both for military and administrative area.

However, looking at the internal conflict of Hosokawa clan, former 10th Shogun Yoshitane Ashikaga attempted to recapture the place of Shogun in alliance with Ouchi clan, the most wealth governor of Suo province (Yamaguchi prefecture). Looking at this, the relationship of Sumimoto Hosokawa and Takakuni Hosokawa became broken, and Takakuni changed to the side of Yoshitane Ashikaga and Ouchi clan.

Short term glory and death of Motonaga Miyoshi

In 1508, Sumimoto Hosokawa and Yukinaga Miyoshi lost their government and were expelled from Kyoto city. After that Sumimoto and Yukinaga struggled against Takakuni Hosokawa and Ouchi army and once recovered Kyoto city, but soon was deprived. At this time Yoshitane Ashikaga came back to the Shogun position, and Takakuni Hosokawa also became the leader of Hosokawa clan.

In 1520, looking at the return of Ouchi army which was the military source of Takakuni Hosokawa, Sumimoto Hosokawa and Yukinaga Miyoshi again landed to the mainland to recover Kyoto city. Sumimoto and Hosokawa once captured Kyoto city, but faced counter attack of Takakuni Hosokawa who was supported by neighbor lords such as Rokkaku clan or Asakura clan, Sumimoto and Yukinaga suffered severe defeat before Takakuni Hosokawa. Yukinaga and his sons were captured and killed, and Sumimoto soon died in ill.

As a result of this severe defeat, Harumoto Hosokawa (1514-1563), son of Sumimoto Hosokawa and Motonaga Miyoshi ( 1501-1532), the grandson of Yukinaga Miyoshi, waited for the opportunity of revenge from Awa province. In 1526, Kataharu Yanagimoto (?-1530) whose younger brother was unreasonably killed by Takakuni Hosokawa raised his army against Takakuni. Kataharu broke the subjugation army from Takakuni, and the army of Takakuni collapsed.

Revenge from other side of straight

Looking at this opportunity, Harumoto Hosokawa and Motonaga Miyoshi landed to Sakai city where prospered as a largest trade port, and established their government placing Yoshitsuna Ashikaga (1509-1573), the son of former Shogun Yoshitane Ashikaga. Motonaga and Kataharu beat Takakuni Hosokawa and captured Kyoto city in 1527, and once established their government.

But this time Motonaga Miyoshi and Kataharu Yanagimoto broke then Motonaga returned to Awa province. Takakuni Hosokawa who looked at this marched to Kyoto city being supported by Rokkaku clan or Asakura clan, and Kataharu was assassinated by the enemy.

Harumoto Hosokawa forced to the corner called Motonaga Miyoshi and made decisive battle against Takakuni Hosokawa at current Amagasaki city. Takakuni had larger army but was confused by the betrayal of Akamatsu army who was under Uragami army but had a grudge against Uragami clan, thus Motonaga Miyoshi totally broke the army of Takakuni Hosokawa. This battle occurred in 1531 is called as "Daimotsu-Kuzure", and Takakuni was captured then killed.

Second time loss of clan leader

Now the government of Harumoto Hosokawa and Motonaga Miyoshi might be the legitimate one, but Harumoto thought to coordinate with present Shogun Yoshiharu Ashikaga (1511-1550). Harumoto and Motonaga broke at this point, and Motonaga siege Iimoriyama castle held by Nagamasa Kizawa (1493-1542), the retainer of Hosokawa clan and supporter of Harumoto Hosokawa in 1532.

Motonaga forced Iimoriyama castle to the corner of fall, but at this time as a result of plot of Harumoto Hosokawa. But thousand of Ikko Ikki army formed by the believers of Jyodo-Shinshu denomination of Japanese Buddhism suddenly attacked Miyoshi army from backside, as Motonaga Miyoshi supported Hokkeshu denomination, the rival of Jyodo-Shinshu. Motonaga killed himself in resentment succeeding to his grandfather and father, and Miyoshi clan returned to Awa province and waited for another chance.

Transition of holders

During this period, Onishi castle worked as a branch castle of Hakuchi castle and supported the continuous expedition of Miyoshi clan economically. After the collapse of Miyoshi government in 1560's and retreat from central area, Onishi clan still kept Onishi castle, but in 1577 Motochika Chosokabe (1539-1599), the warlord of Tosa province who aimed unity of Shikoku island, beat Onishi clan then captured Hakuchi castle and Onishi castle.

Motochika Chosokabe significantly reformed Hakuchi castle as a headquarter of his expedition, and Onishi castle might be kept as a branch castle of Hakuchi castle toward east. Same as Miyoshi clan, Chosokabe clan deprived economic resource of Miyoshi clan and went down Yoshino-gawa river defeating Miyoshi army, and finally deprived Shozui castle, the remaining main base of Miyoshi clan in 1582.

In 1585, because of the Shikoku campaign of central ruler Hideyoshi Toyotomi (1537-1598), Motochika Chosokabe surrendered to Hideyoshi and lost Awa province. Hachisuka clan which was the veteran retainer of Hideyoshi was appointed as the lord of Awa province, and Hachisuka clan improved Onishi castle as one of the nine branch castles at the western edge of the province.

Structure of Onishi castle and afterward

As the castle site is a long and narrow peninsular like terrace, Onishi castle might consist of several terraces just vertically divided by dry moat. As the outside terrain of the castle at west side is slightly higher than inside, basement of turret protected by stone walls might be built inside the outer dry moat, to fire the enemy from higher place.

Stone wall of this basement partially remain as a basement of kindergarten building for about 10 meter long. Only lower part remains but size of stones and pile up of the corner are advanced one compared with other branch castles of Hachisuka clan such as Ichinomiya castle or Mugi castle, and this shows the importance of Onishi castle in the domain.

Hachisuka clan placed its important retainer Kazunaga Ushida (?-?) as the commander of Onishi castle, but the castle was abolished under Ikkoku Ichijo Rei (one castle one domain rule) published in 1615. After the abolishment of castle, castle town as the center of local commerce and transportation, and old style merchant houses still remain around castle site.

Now Castle site is used as ground of schools, and most part of structure of the castle except for the stone wall is lost. But steep cliff at both side of the height clearly shows the existence of the castle. The flow of Yoshino-gawa river seen from castle site reminds long journey of Miyoshi clan rose from small mountainous road to a powerful clan of Muromachi Shogunate, as a prototype of succeeding pre-modern governments.