Tokutan Castle (Iwate Prefecture) Complete Guide: History and Highlights of the Last Ancient Fort of the Heian Period
What is Tokutan Castle?
Tokutan Castle (Tokutan-jo/Tokutan-no-ki) is an ancient fort from the early Heian period, located in Tokuta, Yahaba-cho, Shiwa-gun, Iwate Prefecture. Constructed around 812 AD (Kōnin 3), it holds historical significance as the last fort built by the Yamato court on the northern border of Mutsu Province.
Designated a national historic site on August 5, 1969 (Showa 44), it is currently being developed as a historic park. With its unique origins as a relocation from Shiwa Castle (Morioka City), it is highly valued from both archaeological and historical perspectives as a valuable site representing a turning point in the administration of ancient Tohoku.
Basic Information
- Name: Tokutan Castle (Tokutan-jo/Tokutan-no-ki)
- Location: Nishitokuda, Yahaba-cho, Shiwa-gun, Iwate Prefecture
- Former Province: Mutsu Province
- Classification/Structure: Ancient castle fortification, square castle
- Size: Approximately 350 meters per side (approximately 3 cho square)
- Year of Construction: Around 812 (Kōnin 3)
- Builder: Funya no Watamaro
- Historical Site Designation: National Historic Site (Designated August 5, 1969)
- Managing Organization: Yahaba Town
Historical Background of Tokutan Castle
History of Relocation from Shiwa Castle
To understand the establishment of Tokutan Castle, it is necessary to know the history of its predecessor, Shiwa Castle. Shiwa Castle was an ancient fortified settlement built in 803 (Enryaku 22) approximately 10 kilometers north of Izawa Castle (present-day Ota, Morioka City), functioning as a frontline base on the northern border of Mutsu Province.
However, because Shiwa Castle was located in a low-lying area near the banks of the Shizukuishi River, it was frequently damaged by floods. To solve this serious flood problem, in 811 (Kōnin 2), Funya Watamaro, the Shogun, proposed to the Imperial Court that Shiwa Castle be relocated, and his proposal was approved.
Construction Process
Around March 812 (Kōnin 3), construction of a new fortified settlement began approximately 10 kilometers south of Shiwa Castle, in present-day Tokuda, Yahaba Town. It is said that approximately 2,000 soldiers were mobilized for this construction.
It is believed that some of the buildings and materials from Shiwa Castle were dismantled and reused in the new castle. This relocation and construction was not merely a change of location, but signified a reorganization of military and administrative centers on the northern frontier of Mutsu Province.
The name of Tokutan Castle is recorded alongside Izawa Castle in an official document from 815 (Kōnin 6), and at this point, the name of Shiwa Castle disappears from historical records. From this, it is estimated that Tokutan Castle was completed around 814 (Kōnin 5).
Significance as the Last Fortress under the Ritsuryo System
Tokutan Castle is noteworthy as the last fortress built by the Yamato court in Mutsu Province. In 811 (Kōnin 2), when Fumuro no Watamaro subdued Nisatai and Hei, the fighting with the Emishi subsided, and a period of peaceful rule began.
From this point onward, the court ceased construction of new fortresses and shifted to a policy of maintaining and utilizing existing fortresses. Tokutan Castle is a fortified settlement built during this transitional period, and it can be considered a symbolic site representing the shift from military expansion to administrative governance in ancient Tohoku.
Structure and Scale of Tokutan Castle
Overall Layout
Tokutan Castle is located on a slightly elevated area (low plateau) in the alluvial plain and has a nearly square plan. Measuring approximately 350 meters (about 3 cho) on each side, it exhibits the typical structure of an ancient fortified settlement surrounded by outer fortifications.
Gate remains have been confirmed in the center of each side of the outer fortification, indicating that it was a castle open to all four sides. Furthermore, the remains of watchtowers have been discovered at intervals of approximately 200 shaku (about 60 meters) along the outer fortification, clearly indicating that these were defensive structures.
Government Office Site
The government office was located in the central part of the castle. The site of the government office is located south of the current Tokutan Elementary School (formerly Tokutan Minami Elementary School), and this location is believed to have been the administrative and military center of the fortified settlement.
The administrative office was the most important facility within the castle grounds, where provincial governors and military commanders conducted their duties and important ceremonies and meetings were held. At the site of the administrative office at Tokutan Castle, remains such as the remains of a post-and-beam building have been discovered.
Outer Enclosures
The outer enclosure is presumed to have consisted of earthworks, fences, and moats. Excavations have confirmed the remains of the western gate of the outer enclosure, providing valuable data on the gate’s structure and size.
The western gate of the outer enclosure is located west of the national highway, and its remains are still preserved. Numerous important remains for understanding the castle’s defensive system have been discovered around this gate.
Results of Excavations
Previous Investigations
Multiple excavations have been conducted at the Tokutan Castle site from the Showa era through the Heisei and Reiwa eras. These investigations have gradually revealed the structure, size, age, and function of the castle.
The excavation has uncovered remains such as building foundations, fence lines, gates, watchtowers, and wells, providing a concrete picture of the ancient castle complex. In particular, the investigations around the administrative office site and the outer fortifications have yielded important results in understanding the overall structure of Tokutan Castle.
Excavated Artifacts
The excavation has yielded a diverse range of artifacts. Among the pottery, many everyday vessels such as Sue ware and Haji ware are found, offering insights into daily life at the time. Wooden artifacts have also been found in excellent condition, providing valuable information about ancient woodworking techniques.
Of particular note is the wooden helmet unearthed from the well site. This discovery is important evidence that the castle complex had a military function. The wooden helmet is remarkably well-preserved and is valued as a valuable artifact for the study of ancient weaponry.
Other artifacts, including iron objects, stone objects, and animal bones, have also been unearthed. These artifacts are displayed and stored at the Yahaba Town Historical and Folk Museum.
Characteristics of the Building Remains
The building remains confirmed by the excavation survey are mainly those of post-and-beam buildings. Post-and-beam buildings are constructed by digging holes in the ground and erecting posts, a construction method widely used in ancient government buildings and warehouses.
Based on the arrangement and scale of the buildings, functional differentiation into areas such as government offices, barracks, and warehouses is presumed. In particular, the presence of large buildings used for ceremonies and official duties is assumed in the government office area, allowing us to interpret the expression of authority within the ancient fortifications.
Highlights of Dedan Castle
Historical Park
The Dedan Castle ruins are currently being developed as a historical park. The area centered around the government office remains has been transformed into a park, aiming for the preservation and utilization of the remains.
Information boards are installed within the park, providing detailed explanations of the history and structure of Dedan Castle. Furthermore, some of the remains confirmed by the excavation surveys are displayed, allowing visitors to imagine the appearance of the fortifications in their heyday.
The historical park is an open space that can be freely explored and is a popular place of relaxation for local residents. During cherry blossom season, visitors can enjoy beautiful scenery, making it a spot where you can enjoy both historical walks and nature appreciation.
Outer Wall West Gate Ruins
The remains of the Outer Wall West Gate are preserved on the west side, across National Route 4. Here, you can see the remains of an ancient gate up close and gain a concrete understanding of the castle’s defensive system.
The area around the West Gate remains is relatively well-preserved, and traces of fences and moats can be seen. Information boards are also installed, allowing visitors to learn about the gate’s function and structure while exploring.
Well Ruins (Site where a wooden helmet was unearthed)
The well ruins where a wooden helmet was unearthed are also an important point of interest. This well served as a facility supplying water for daily life within the castle walls, and is also an archaeologically significant site where valuable artifacts were discovered.
Numerous wooden artifacts and pottery, in addition to a wooden helmet, have been unearthed from the well site, providing valuable information about the lives and military activities of ancient people.
Yahaba Town Historical and Folk Museum
Facility Overview
The Yahaba Town Historical and Folk Museum is located next to the Tokutan Castle ruins. This museum introduces the history and culture of Yahaba Town, focusing on artifacts unearthed from the Tokutan Castle ruins.
The museum displays pottery, wooden artifacts, and iron artifacts unearthed from Tokutan Castle, allowing visitors to learn about the results of the excavation in detail. The display of the actual wooden helmet is a must-see, offering a valuable opportunity to observe ancient weaponry up close.
Exhibits
The permanent exhibition systematically introduces the history, structure, and unearthed artifacts of Tokutan Castle. Models, diagrams, and photographic panels are also abundant, making the exhibits visually easy to understand.
Furthermore, the relationship with Shiwa Castle and the role of fortifications in ancient Tohoku are explained, allowing visitors to understand Tokutan Castle within a broader historical context. The museum regularly holds special exhibitions, showcasing the latest archaeological findings and related themes.
Visitor Information
The Yahaba Town Historical and Folk Museum is a must-visit facility when visiting the Tokutan Castle Ruins. Gaining background knowledge at the museum before visiting the site will significantly deepen your understanding of the ruins.
For details on opening hours, closing days, and admission fees, please check the official Yahaba Town website. It is recommended to inquire in advance, as guided tours by curators may be available.
Access Information
Public Transportation
- JR Tohoku Main Line: Approximately 5 minutes by car or 20 minutes on foot from Yahaba Station
- Bus: Iwate Kotsu buses are also available (within walking distance of the nearest bus stop)
Yahaba Station is two stops from Morioka Station, making access relatively easy. A taxi from the station will get you there quickly.
By Car
- Tohoku Expressway: Approximately 10 minutes by car from Yahaba Smart Interchange
- General Roads: Approximately 20 minutes by car from central Morioka City, along National Route 4
Parking is available adjacent to the Yahaba Town Historical and Folk Museum. There are also parking spaces around the historical site park, making it convenient for visitors arriving by private car.
Related Historical Sites in the Surrounding Area
Shiwa Castle Ruins (Morioka City)
The Shiwa Castle Ruins, the predecessor of Tokutan Castle, are located in Ota, Morioka City, and are designated as a national historical site. The outer southern gate and earthen wall have been restored, allowing visitors to experience the magnificent appearance of the ancient castle.
Visiting both Tokutan Castle and Shiwa Castle together provides a clearer understanding of the relocation history and the differences between the two castles. The Shiwa Castle Ruins have been developed into the Shiwa Castle Ancient Park, which also features comprehensive guidance facilities.
Izawa Castle Ruins (Oshu City)
Izawa Castle, built in 802 AD by Sakanoue no Tamuramaro, was the largest ancient castle in Mutsu Province and is designated a national historic site. It functioned as a rear base for Tokutan Castle and Shiwa Castle, playing a central role in the administration of the northern border of Mutsu Province.
The Izawa Castle ruins are large in scale and offer impressive sights, including a reconstructed administrative office. Visiting both Izawa Castle and Tokutan Castle allows for a better understanding of the ancient castle network.
Morioka Castle Ruins (Morioka City)
The Morioka Castle ruins (Iwate Park), dating from the early modern period, are also relatively close to Tokutan Castle. This is a valuable route for tracing the evolution of castles in Iwate Prefecture from ancient to early modern times.
Takamizudera Castle Ruins (Shiwa Town)
The Takamizudera Castle ruins, a medieval mountain castle, are also located within Shiwa District. It is an interesting historical site for comparative research on the changes in castles from ancient fortifications to medieval mountain castles.
Historical Evaluation and Future Prospects of Tokutan Castle
Academic Value
Tokutan Castle is an extremely important archaeological site in the study of ancient Tohoku history. It possesses many academic values, including its unique establishment process (relocation from Shiwa Castle), its historical position as the last castle under the Ritsuryo system, and its well-preserved state.
The results of archaeological excavations have greatly contributed to the elucidation of the structure and function of ancient castles and fortifications, and the military and administrative systems of ancient Tohoku. Furthermore, the excavated artifacts are valuable resources for understanding the material culture and technological level of ancient times.
Preservation and Utilization
Yahaba Town is actively working on the preservation and utilization of the Tokutan Castle site. In addition to developing it as a historical park, the town is implementing multifaceted utilization projects, including exhibitions at the Historical and Folk Museum, installation of explanatory signs, and creation of pamphlets.
It is expected that continued archaeological excavations will further clarify the overall picture of Tokutan Castle. Furthermore, plans are underway to create a more attractive historical park through the restoration and development of remains and the enhancement of experiential learning programs.
Utilization as a Local Resource
Tokutan Castle Ruins are a valuable historical and cultural resource of Yahaba Town and are being utilized for regional development and tourism promotion. They also play an important role as a site for local history learning in schools, contributing to the formation of the region’s identity.
Visits from ancient history enthusiasts and castle lovers are increasing, and it is attracting attention as part of the “Ancient Castle Tour” connecting Tokutan Castle, Shiwa Castle, and Izawa Castle.
Summary
Tokutan Castle is an ancient castle built around 812 AD (Kōnin 3), and is a historically important site as the last castle built by the Yamato court in Mutsu Province. It has a unique history of establishment, having been relocated due to flooding at Shiwa Castle, and symbolizes a turning point in the administration of ancient Tohoku.
It is a square castle with sides of approximately 350 meters, and archaeological excavations have confirmed the remains of the government office, outer gate, watchtower, and well. The excavated pottery and wooden artifacts, especially the wooden helmets, are valuable resources for understanding ancient life and military affairs. Currently designated as a national historic site, it is being developed as a historic park. The adjacent Yahaba Town Historical and Folk Museum displays excavated artifacts, allowing visitors to learn about the history of Tokutan Castle in detail.
With easy access—approximately 5 minutes by car from JR Yahaba Station and 10 minutes from the Tohoku Expressway Yahaba Smart Interchange—visiting Tokutan Castle along with other ancient castles and fortifications in the area, such as Shiwa Castle and Izawa Castle, provides a deeper understanding of ancient Tohoku history.
Tokutan Castle ruins, which convey the spirit of the Heian period, are a recommended historic site not only for history enthusiasts but also for anyone who wants to experience the history and culture of Iwate Prefecture.
