A Thorough Explanation of the History and Remains of Daisai Castle – Three Daisai Castles in Izumo, Awa, and Iyo
Castles bearing the name Daisai Castle existed in multiple regions throughout Japanese history. Each had a different historical context, builder, and historical role, making them important for understanding the history of Japanese castles. This article provides a detailed explanation of the history, structure, and current state of Izumo Daisai Castle in Unnan City, Shimane Prefecture, Awa Daisai Castle in Miyoshi City, Tokushima Prefecture, and Iyo Daisai Castle in Imabari City, Ehime Prefecture.
Daisai Castle, Izumo Province (Unnan City, Shimane Prefecture)
Overview and Location
Daisai Castle in Izumo Province is a mountain castle located in Kamo-cho, Unnan City, Shimane Prefecture. Built on a highly isolated hill with a relative height of 130 meters, it was an important military base in the San’in region during the Sengoku period. This castle was counted as one of the Amago Ten Banners and played an important role within the Amago clan’s sphere of influence.
In terms of location, it was situated on high ground overlooking the surrounding area, a strategic position that allowed for early detection of enemy movements. The castle’s layout, making maximum use of the isolated hilltop terrain, exhibits typical characteristics of a medieval mountain castle.
History and Changes in Castle Lords
The exact construction date of Onishi Castle is unclear, but one theory suggests it was built by Kurakake Hisamitsu during the Tenbun era (1532-1555) of the Sengoku period. During the Amago clan’s rule, the Onishi clan served as its base.
The Onishi clan was one of the Amago clan’s powerful retainers and contributed to maintaining the Amago clan’s power as one of the “Ten Amago Castles.” The “Ten Amago Castles” refer to the ten branch castles protecting Gassan-Toda Castle, the Amago clan’s main base, and Onishi Castle held an important position among them.
After the Amago clan’s defeat in their conflict with the Mori clan, Onishi Castle also disappeared from the historical stage. It is believed that the castle lost its functionality during the wars of the Eiroku and Tensho periods.
Structure and Layout
Onishi Castle has the typical structure of a medieval mountain castle, with multiple baileys arranged around the main enclosure. The defensive system, utilizing the 130-meter elevation difference, was a major obstacle for attacking forces.
Defensive facilities such as moats, earthworks, and steep slopes, characteristic of mountain castles, were incorporated, allowing for effective defense even with a limited number of personnel. The main enclosure offered a panoramic view of the surrounding plains, also serving a military surveillance function.
Current Status and Remains
Currently, remains such as baileys and moats remain at the Onishi Castle site. The basic structure of a mountain castle can be confirmed in the topography, making it a historical site visited by castle enthusiasts and history buffs. However, no significant structures such as stone walls have been found, strongly retaining the characteristics of an earthen castle.
While some parts of the access path are maintained, the steep terrain characteristic of mountain castles requires appropriate equipment and physical fitness for a visit. ## Onishi Castle, Awa Province (Miyoshi City, Tokushima Prefecture)
Overview and Alternate Names
Onishi Castle in Awa Province was a flatland castle located in Ueno, Ikeda-cho, Miyoshi City, Tokushima Prefecture. It was called “Onishi” because it was located at the westernmost point of Awa Province, and it was also known as Ikeda Castle. The area around the current Ikeda Kindergarten corresponds to the former castle grounds.
This castle played an important role as one of the nine castles of Awa until the early Edo period. Built on a plateau approximately 20 meters high overlooking the Yoshino River, its layout utilized the natural fortifications of the river-facing side (a steep cliff) and the southern side (a steep slope).
History and Construction History
The history of Onishi Castle dates back to the Jokyu War of 1221. Ogasawara Nagakiyo, who distinguished himself in this rebellion, was appointed governor of Awa Province, and his son, Ogasawara Nagatsune, entered the province as deputy governor. Nagatsune built Onishi Castle and attacked and destroyed Chausuyama Castle, the main castle of the former governor Sasaki clan, who sided with Emperor Go-Toba in the Jokyu War.
With this castle construction, the Ogasawara clan established their control over western Awa Province. From the Kamakura period to the Muromachi period, Onishi Castle continued to function as an important base for governing Awa Province.
During the Sengoku period, it came under the influence of the Miyoshi clan, and later under the rule of the Chosokabe clan. After Hashiba Hideyoshi’s conquest of Shikoku in 1585, it became part of the territory of the Hachisuka clan. Ushida Kamonnojo, a retainer of Hachisuka Iemasa, served as the castle lord, and it played a part in the domain’s administration as one of the nine castles of Awa.
Changes in Castle Lords
The lords of Onishi Castle changed over time. Beginning with the Ogasawara clan during the Kamakura period, the area was ruled by local samurai groups from the Nanboku-cho period to the Muromachi period. During the Sengoku period, it came under the influence of the Miyoshi clan, and subsequently, the rulers shifted to the Chosokabe clan and then the Hachisuka clan.
In the Edo period, a vassal of the Hachisuka clan was appointed as the castle lord, and it functioned as a base for regional control. However, with the “One Castle Per Province” decree of the Genna era, many branch castles were abandoned, and it is believed that Onishi Castle gradually lost its function.
Structure and Defensive Facilities
Onishi Castle was a flatland castle that cleverly utilized the plateau topography, with the Yoshino River serving as a natural moat. The natural terrain, including the river-facing section and the steep southern slope, served as the main defensive lines, and the design minimized artificial defensive facilities.
Multiple baileys were arranged within the castle grounds, efficiently distributing living and defensive spaces. Stone walls were partially constructed, exhibiting characteristics of castle architecture from the transitional period between the medieval and early modern periods.
Existing Remains
Currently, much of the Onishi Castle site is urbanized, with facilities such as Ikeda Kindergarten built on the site. However, stone walls remain below the kindergarten, preserving the appearance of the castle former.
These stone walls are valuable as one of the few remaining structures of Onishi Castle and are an important historical site that tells the story of the region’s history. Although complete preservation is difficult, the partially remaining remains allow us to infer the castle’s structure from its heyday.
Onishi Castle, Iyo Province (Imabari City, Ehime Prefecture)
Overview and Location
Onishi Castle in Iyo Province was a mountain castle located in Imabari City, Ehime Prefecture (formerly Onishi Town, Ochi District). Built on a mountain west of the Donkawa Seseragi Exchange Center, it functioned as the residence of a powerful local samurai.
Although smaller in scale compared to Onishi Castles in Izumo and Awa, it played an important role as a military base in the region.
History and Lord
Iyo-Oonishi Castle is believed to have been the residence of Monma Uemon-no-jo, a retainer of Ochi Michiyoshi, the lord of Takagamori Castle, and a member of the Murakami clan, around the Tensho era (1573-1592).
As the castle lord was a member of the Murakami clan, known for their naval power, it is an interesting example illustrating the connection between maritime and land forces in this region.
Amidst the changing political landscape of Shikoku at the end of the Sengoku period, Iyo-Oonishi Castle also disappeared from the historical stage. It is believed that, along with many other small and medium-sized castles that were abandoned after Toyotomi Hideyoshi’s conquest of Shikoku, Onishi Castle shared the same fate.
Current State of Remains
Regarding the remains of Iyo-Oonishi Castle, it is thought that remnants such as baileys and moats remain as topographical features, but detailed survey records are limited. Buried within the forest, it is difficult to reconstruct its original appearance.
Comparison of the Three Onishi Castles
Construction Period and Background
Izumo Onishi Castle was built during the Sengoku period within the Amago clan’s sphere of influence. Awa Onishi Castle was built after the Jōkyū War during the Kamakura period. Iyo Onishi Castle was built by local samurai at the end of the Sengoku period. Each castle has a different historical background.
Castle Size and Structure
Izumo Onishi Castle is a full-fledged mountain castle with a relative height of 130 meters. Awa Onishi Castle is a flatland castle with a relative height of 20 meters. Iyo Onishi Castle is a small mountain castle. Each castle differs in location and size. This reflects the topographical conditions and military needs of each region.
Historical Role
Izumo Onishi Castle played an important role in the Sengoku period history of the San’in region as one of the Amago Ten Castles. Awa Onishi Castle played an important role as one of the Nine Castles of Awa during the transition from the medieval to the early modern period in Shikoku. Iyo Onishi Castle served as a base for regional control.
Points to Note When Visiting Onishi Castle
Access
Awa Onishi Castle Ruins (Miyoshi City, Tokushima Prefecture) are accessible in about 10 minutes on foot from Awa-Ikeda Station on the JR Dosan Line. Located in an urban area, it is a relatively easy historical site to visit.
Izumo Onishi Castle Ruins (Unnan City, Shimane Prefecture) are mountain castles, so climbing them requires time and physical strength. It is recommended to prepare appropriate climbing equipment and check the weather before visiting.
Iyo Onishi Castle Ruins (Imabari City, Ehime Prefecture) are also mountain castles, and prior information gathering and preparation are necessary before visiting.
Points to Note When Visiting
At Awa Onishi Castle, the main highlight is the stone wall remaining below the kindergarten. You can also enjoy the view from the city and imagine the view from the castle in its heyday.
At Izumo Onishi Castle, you can see the remains of the castle, such as the layout of baileys and moats, which are characteristic of mountain castles. The view from the climbing path is magnificent, allowing you to appreciate the ingenuity of the location selection for castles during the Sengoku period. ### Current Status of Preservation and Utilization
Each Onishi Castle site is in a different state of preservation. While much of the remains of Awa Onishi Castle have been lost due to urbanization, the remaining stone walls are recognized as a regional historical heritage. Izumo Onishi Castle’s remains are preserved within a forest and are in relatively good condition.
Investigations and preservation activities by local historical research groups and castle enthusiasts are ongoing, and it is hoped that these remains will be passed down to future generations.
Historical Significance of Onishi Castles
Position in Medieval Castle History
The three Onishi Castles are important examples for understanding the history of Japanese castles, representing the transition period from the medieval to the early modern period in their respective regions. They specifically illustrate the transition from mountain castles to flatland castles, changes in regional power, and the development of military technology.
Importance in Regional History
Each Onishi Castle functioned as a political and military center in its respective region. In Izumo, it played a significant role in maintaining the power of the Amago clan; in Awa, in the transition of power from local lords to early modern daimyo; and in Iyo, in the activities of regional samurai groups.
Cultural Value
Although the remaining structures are limited, each Onishi Castle site is a valuable cultural asset that conveys the history of the region. The remains, such as stone walls, baileys, and moats, are important historical materials that convey the castle-building techniques and defensive philosophies of the time.
Related Castles and Historic Sites
Amago Ten Castles and Izumo Onishi Castle
Izumo Onishi Castle was one of the Amago Ten Castles, part of the Amago clan’s castle network centered around Gassan Tomita Castle. Other Amago Ten Castles included Shiraka Castle, Mitoya Castle, and Akana Castle, and these worked together to protect the Amago clan’s sphere of influence.
The Nine Castles of Awa Province and Awa Onishi Castle
Awa Onishi Castle, as one of the nine castles of Awa Province, played a vital role in the Hachisuka clan’s rule over Awa. The other nine castles included Ichinomiya Castle, Ushiki Castle, and Ebisuyama Castle, all strategically located Awa Province to support the domain’s administration throughout.
The Murakami Naval Force and Iyo Onishi Castle
The fact that the lord of Iyo Onishi Castle was a member of the Murakami clan is an interesting example illustrating the relationship between maritime powers in the Seto Inland Sea and land-based castles. The Murakami Naval Force operated from bases such as Noshima Castle and Kurushima Castle, expanding its influence both on land and sea.
Summary
The three castles bearing the name “Onishi Castle,” each representing a different region, era, and background, demonstrate the diversity of castles during Japan’s transition from the medieval to the early modern period. While each possessing distinct characteristics—a mountain castle in Izumo, a hilltop castle in Awa, and a regional base in Iyo—all played important roles in their respective regional histories.
Although only a limited number of remains survive today, these castle ruins are valuable cultural heritage sites that tell the story of the region’s history. For enthusiasts and history buffs, a visit to the Onishi Castle ruins will be a precious opportunity to experience the history of Japanese castles.
It is hoped that further preservation efforts and research by the local community will reveal even more about the historical value of Onishi Castle. It is our important responsibility to carefully preserve the small and medium-sized castle ruins scattered throughout Japan and pass them on to future generations.
