Kannai Castle Ruins (Nishiueda-cho, Takamatsu City): The History of a Medieval Mountain Castle in Sanuki and the Kannai Clan
Located in Kamihigashikannai, Nakatani, Nishiueda-cho, Takamatsu City, Kagawa Prefecture, the Kannai Castle Ruins are an important historical site that tells the story of the medieval history of Sanuki Province. This hill castle, believed to have been built by the Kannai clan who ruled this area from the Nanboku-cho period to the Muromachi period, still retains well-preserved remains such as earthworks and baileys, conveying the castle construction techniques and regional governance of the time.
This article provides a comprehensive explanation of this Sanuki mountain castle, including its historical background, detailed castle structure, the results of archaeological excavations, and related surrounding sites.
Location and Geographical Characteristics of Kannai Castle
Kannai Castle is located in the hilly area of Nishiueda-cho, Takamatsu City, and is a hill castle built on the top of a hill approximately 89 meters above sea level. With a relative height difference of about 20 meters, it is strategically situated overlooking the surrounding plains. ### Geographical Importance
Located in the central part of Sanuki Province, this area has played an important role as a transportation hub since ancient times. The location of Kannai Castle held strategic value in the following ways:
- Securing Visibility: From the hilltop, the surrounding plains could be seen, allowing for early detection of approaching enemies.
- Defensive Advantage: Functioning as a natural fortress utilizing the difference in elevation.
- Monitoring Transportation Routes: Its location allowed for monitoring of major roads within Sanuki Province.
- Securing Water Sources: Water sources existed in the surrounding area, providing a defense during sieges.
The topography of Kagawa Prefecture is characterized by a gentle slope from the Sanuki Mountains towards the Seto Inland Sea, and hill castles like Kannai Castle were a typical form of castle construction in medieval Sanuki.
History of the Kannai Clan and the Castle
Origin and Power of the Kannai Clan
The Kannai clan was a local powerful family in Sanuki Province that ruled this region from the Kamakura period to the Muromachi period. While detailed genealogical records are limited, it is confirmed that the Kannai clan held significant power in this area during the Nanboku-chō period (Northern and Southern Courts period).
Construction Date and Historical Background
The exact construction date of Kannai Castle is uncertain, but it is believed to have been built by the Kannai clan during the Nanboku-chō period (1336-1392). This period was a time of nationwide turmoil, and in Sanuki Province, the forces of the Southern and Northern Courts were fiercely opposed.
During the Nanboku-chō period, the Hosokawa clan held power as the shugo (provincial governor) of Sanuki Province, and local powerful families struggled to survive amidst the complex political situation. It is thought that the Kannai clan, under these circumstances, fortified their castle to protect their territory.
From the Muromachi Period to the Sengoku Period
During the Muromachi period, Sanuki Province remained under the rule of the Hosokawa clan. However, during the Sengoku period (Warring States period), various forces, including the Miyoshi and Chōsokabe clans, vied for control of Sanuki. While there are no clear records of the role Kannai Castle played during these conflicts, the condition of the castle remains indicates that it was in use for a certain period.
Kannai Castle’s Layout and Structure
Basic Structure: Single-Enclosure Castle
Kannai Castle is characterized by being almost a single-enclosure castle. This means it has a relatively simple structure centered around the main enclosure (Honmaru), but in reality, it consists of two main enclosures (kuruma): the Honmaru and the Ninomaru.
Honmaru (Main Enclosure)
- Location: The elevated earthen platform on the north side
- Function: Used as the lord’s residence and command post
- Features: The highest elevation, a crucial defensive location
Ninomaru (Second Enclosure)
- Location: Located south of the Honmaru
- Features: Equipped with an earthen rampart, enhancing defensive capabilities
- Function: Estimated to have functioned as a vassal quarters and storage area for supplies
Details of Defensive Facilities
Earthen Ramparts
Earthen ramparts are an important defensive facility of Kannai Castle. In particular, the earthen rampart attached to the Ninomaru is a clearly visible structure even today. Earthworks served the following functions:
- Physically preventing enemy intrusion
- A defensive wall against arrows and stones
- A screen for concealing the interior of the enclosure
- A symbolic function demonstrating the castle’s grandeur
Earthworks in medieval castles of Sanuki were constructed according to the local soil and topography, and it is believed that the earthworks of Kannai Castle were also constructed by piling up local soil.
Moats
Moats, an important defensive structure in hill castles, are also believed to have existed at Kannai Castle. Moats are structures that cut off enemy intrusion routes by artificially cutting the ridge. This was a common defensive method in mountain castles of medieval Sanuki.
Castle Area Scope
The castle area of Kannai Castle was relatively compact, with the main part concentrated in a limited space at the top of the hill. This is a characteristic seen in early medieval castles, indicating that it was more of a base for regional control than a place to prepare for large-scale battles.
Excavation and Archaeological Findings
Investigation by Takamatsu City Board of Education
The Takamatsu City Board of Education has conducted an excavation survey of the Kannai Castle ruins, and the results have been compiled in the “Takamatsu City Archaeological Site Excavation Report” (Takamatsu City Buried Cultural Properties Survey Report No. 178).
This investigation has yielded the following findings:
- Confirmation of the castle’s structure and extent
- Construction methods of earthworks and baileys
- Dating based on excavated artifacts
- Period of use and changes over time
Excavated Artifacts and Dating
The excavation survey unearthed artifacts from the medieval period, confirming that the castle dates from the Nanboku-cho period to the Muromachi period. The excavated artifacts include the following:
- Everyday pottery such as Haji ware and Sue ware
- Fragments of medieval pottery
- Iron products (nails, arrowheads, etc.)
- Traces of building materials
These artifacts are valuable resources that tell the story of daily life and military activities within the castle.
Kannai Family Cemetery and Stone Pagoda Group
Kannai Family Cemetery as a Related Archaeological Site
The Kannai Family Cemetery Stone Pagoda Group is located around the site of Kannai Castle. This cemetery contains stone structures such as Hokyoin-to (a type of Buddhist pagoda), and is believed to be the burial place of the Kannai family.
Hokyoin-to are a type of Buddhist pagoda that were widely erected from the Kamakura period to the Muromachi period and were used as memorial towers. The stone pagoda group at the Kannai Family Cemetery is important material for understanding the faith and funeral culture of the Kannai family.
Characteristics of the Stone Pagodas
The stone pagodas in the Kannai family cemetery have the following characteristics:
- Period: Spanning from the Kamakura period to the Edo period
- Form: A variety of stone structures, primarily Hōkyōintō (treasure chest-shaped pagodas)
- Condition: Although showing signs of age-related deterioration, they remain relatively well-preserved
- Historical Value: Tells the story of the Kannai family lineage and local history
These stone pagodas, along with Kannai Castle, are important cultural heritage sites that convey the history of the Kannai family and are carefully preserved in the region.
Medieval Castles of Sanuki Province and Kannai Castle
Characteristics of Castles in Kagawa Prefecture
Numerous medieval castles remain in Kagawa Prefecture. Representative examples include:
- Takamatsu Castle (Sanuki Province): One of Japan’s three great water castles, a modern castle from the Edo period
- Marugame Castle: A famous castle with an existing keep
- Hikida Castle: A mountain castle overlooking the Seto Inland Sea
- Katsuga Castle: A representative medieval mountain castle in Takamatsu City
- Yashima Castle: Designated as a national historic site as an ancient mountain castle
Among these, Kannai Castle occupies an important position in the history of castles in Sanuki as a castle of a local powerful family in the early medieval period.
Types of Hill Castles
Hill castles like Kannai Castle were a common castle form in Sanuki Province. By utilizing hills close to the plains, the following advantages were available:
- Convenient for managing territory in peacetime
- Functions as a defensive base in times of emergency
- Reduced construction costs
- Functions as a symbol of regional control
Kannai Castle can be understood as an example of such a typical hill castle of medieval Sanuki.
Current Status of Kannai Castle Ruins
Preservation of the Remains
The current state of Kannai Castle ruins is relatively well-preserved, having escaped development. In particular:
- The earthen platform of the main enclosure
- The earthen rampart of the second enclosure
- The topography of the baileys
- Traces of moats
These can be observed. However, due to the dense vegetation, careful observation is necessary for detailed viewing.
Cultural Property Designation Status
Currently, Kannai Castle Ruins are not designated as a national or prefectural historical site, but they are recognized as an important historical heritage site of Takamatsu City. Their academic value is acknowledged, as they are recorded in the “Takamatsu City Archaeological Excavation Survey Report.”
Access and Visiting
Kannai Castle Ruins are located in Nishiueda-cho, Takamatsu City, and are carefully preserved by local residents. When visiting:
- Consideration for private and managed land
- Protection of historical remains (do not disturb earthworks, do not damage vegetation, etc.)
- Take your trash with you
- Consideration for local residents
These points require attention.
Kannai Castle and the Medieval History of Sanuki
Sanuki during the Nanboku-cho Period
Sanuki Province during the Nanboku-cho period was strongly affected by the nationwide turmoil. The Hosokawa clan was appointed as the shugo (provincial governor), but local powerful families tried to maintain their own power. The Kannai clan was one such family, and Kannai Castle can be said to be a castle that reflects this regional political situation.
Regional Governance during the Muromachi Period
During the Muromachi period, while the rule of the shugo daimyo (provincial governors) strengthened, local powerful families took root in local communities as kokujin lords (local feudal lords). Small to medium-sized castles like Kannai Castle functioned as residences for these kokujin lords, becoming centers of regional politics, economy, and culture.
Changes During the Sengoku Period
During the Sengoku period, Sanuki Province saw a rapid change of rulers, from the Miyoshi clan and the Chosokabe clan to Toyotomi Hideyoshi’s conquest of Shikoku. Many medieval castles were abandoned during this period, and it is likely that Kannai Castle also ended its historical role during this time.
Related Historical Sites in the Surrounding Area
Medieval Ruins in Takamatsu City
Besides Kannai Castle, Takamatsu City has many other medieval ruins:
- Katsuga Castle Ruins: A mountain castle overlooking Takamatsu city.
- Ishikiyooyama Tumulus Cluster: An ancient site, but also used in the medieval period.
- Yashima: The site of the Genpei War, with remnants of Yashima Castle remaining.
Visiting these ruins together will allow for a deeper understanding of Sanuki’s history.
History of Nishiueda Town
Nishiueda Town, where Kannai Castle is located, is an area where people have lived since ancient times. In addition to the ruins of Kannai Castle and the Kannai family cemetery, the area retains various historical resources, making it an important field for local history research.
Significance and Future Challenges of the Kannai Castle Research
Academic Significance
The study of the Kannai Castle ruins is academically important in the following respects:
- Elucidation of the Regional Governance Structure of Medieval Sanuki: As a castle of a local powerful family, it provides clues to understanding the realities of the local community.
- Study of Castle Structure: As a typical example of a hill castle from the early medieval period, it provides material for understanding the changes in castle construction technology.
- History of the Kannai Clan: Elucidation of the realities of a local powerful family with few historical records.
- Archaeological Data: Elucidation of material culture through excavation surveys.
Future Challenges
The study and preservation of the Kannai Castle ruins face the following challenges:
- Detailed Survey: Precise topographic surveying using the latest technology.
- Additional Excavation: Acquisition of new findings through excavation of unexplored areas.
- Excavation of Documentary Historical Materials: Discovery of new historical materials concerning the Kannai clan and Kannai Castle.
- Preservation and Utilization: Appropriate preservation of the remains and utilization as a regional resource.
- Public Awareness and Education: Disseminating information to local residents and tourists
Geospatial Information Authority of Japan Maps and Digital National Land Maps
The location of the Kannai Castle Ruins can be confirmed using maps from the Geospatial Information Authority of Japan and the Digital National Land Map web map service. Using these map services allows you to:
- Understand the precise location
- Understand the surrounding topography
- Confirm access routes
- Understand the relative location to other historical sites
By using the Map Selection function to switch between aerial photographs and topographic maps, you can gain a more three-dimensional understanding of the castle’s location.
Summary
Kannai Castle Ruins are a medieval castle in Sanuki Province, located in Nishiueda-cho, Takamatsu City, Kagawa Prefecture. Built by the Kannai clan during the Nanboku-cho period, this hill castle retains well-preserved remains such as earthworks and baileys, conveying the characteristics of regional rule at the time.
Together with the excavation surveys conducted by the Takamatsu City Board of Education and the surrounding Kannai family cemetery stone monuments, it is a valuable historical site for understanding the history of the Kannai clan and the medieval history of Sanuki. Although not currently designated as a cultural property, its academic value is highly regarded.
Many medieval castles remain in Sanuki Province, including in Marugame City and Takamatsu City, and Kannai Castle holds an important position among them as a castle of a local powerful family. It is a historical site where appropriate preservation and further research are expected.
When visiting Kagawa Prefecture, why not visit not only the famous Takamatsu Castle and Marugame Castle, but also medieval castle ruins rooted in the local community, such as Kannai Castle, and experience the rich history of Sanuki?
