A Thorough Explanation of Moriyama Castle’s History and Highlights | The Owari Castle that Was the Stage of Matsudaira Kiyoyasu’s “Moriyama Collapse”
Moriyama Castle was a Japanese castle located in Ichiba, Moriyama-ku, Nagoya City, Aichi Prefecture. It is known as the site of a major incident known as the “Moriyama Collapse” during the Sengoku period, a place that significantly altered the history of the Mikawa Matsudaira clan. This article provides a detailed explanation of Moriyama Castle’s history, structure, highlights, and access methods.
What is Moriyama Castle? | Overview and Basic Information
Moriyama Castle was a flatland castle built in Moriyama, Owari Province (present-day Ichiba, Moriyama-ku, Nagoya City, Aichi Prefecture). While there are various theories regarding its construction date and builder, it is believed to have been built around the same time as Nagoya Castle, in the early Sengoku period.
The castle was relatively small, measuring 58 meters east-west and 51 meters north-south, with a single moat. However, its historical importance far exceeds its size. In particular, the Moriyama Incident of 1535 (Tenbun 4), in which Matsudaira Kiyoyasu, grandfather of Tokugawa Ieyasu, was murdered by his retainers, holds a significant place in Japanese Sengoku period history.
Origin of the Place Name Moriyama
The oldest record of “Moriyama” being written as “守山” is a memoir by the renga poet Sōchō from 1526 (Daiei 6). Sōchō held a thousand-verse renga gathering at the residence to celebrate Matsudaira Nobusada’s new fiefdom, and composed the opening verse, “Today’s wind blows through the mountains of Moriyama,” referring to Moriyama. This record is considered the first appearance of the place name “Moriyama” in written documents.
History of Moriyama Castle | From Construction to Abandonment
From Construction to Oda Clan Rule
While there are no clear records of the construction of Moriyama Castle, it is believed to have been built by the Oda clan, who ruled Owari Province. In the early Sengoku period, Owari Province was divided among various branches of the Oda clan, and Moriyama Castle functioned as one of their bases.
The lord of the castle at the time was Oda Nobumitsu, the younger brother of Oda Nobuhide (father of Oda Nobunaga). Oda Nobumitsu played an important role in the Oda family’s unification of Owari, and Moriyama Castle was one of their operational bases.
The “Moriyama Collapse” | The End of Matsudaira Kiyoyasu
The most important event in the history of Moriyama Castle is the “Moriyama Collapse,” which occurred on December 5, 1535 (Tenbun 4).
At that time, Matsudaira Kiyoyasu, who had unified Mikawa Province and expanded his power, was planning an invasion of Owari Province and had deployed his forces at Moriyama Castle. Kiyoyasu was the grandfather of Tokugawa Ieyasu and is known as a great hero who unified Mikawa Province at a young age. He was only 25 years old at the time.
However, in the early morning of December 5th, Kiyoyasu was suddenly attacked and killed by his retainer, Abe Yashichiro Masatoyo. This incident, known as the “Moriyama Collapse,” dealt a major blow to the Matsudaira clan’s growing power.
There are various theories regarding Abe Yashichiro’s motive for killing Kiyoyasu. The most plausible theory is that he believed a false rumor that Kiyoyasu was infatuated with the wife of Yashichiro’s father, Abe Sadakichi. However, there are also theories that it was a conspiracy by the Oda clan, and the truth remains shrouded in mystery.
As a result of this incident, the Matsudaira clan, which had been gaining momentum, suddenly fell into chaos, and was forced to weaken during the time of Kiyoyasu’s son, Hirotada (Ieyasu’s father). Without the “Moriyama Collapse,” the history of the Sengoku period might have been significantly different.
From Oda Nobumitsu to Nobunaga’s Brothers
After the Moriyama Collapse, Moriyama Castle returned to the control of the Oda clan. Oda Nobumitsu was later given Nagoya Castle by Oda Nobunaga and moved there.
After Nobumitsu moved to Nagoya Castle, his younger brother, Oda Nobutsugu, became the lord of Moriyama Castle. Later, Oda Nobutoki, a younger brother of Oda Nobunaga, became the lord.
Oda Nobutoki was Nobunaga’s younger brother by the same mother and played a certain role as the lord of Moriyama Castle, but is believed to have died in the Battle of Okehazama in 1560 (Eiroku 3) fighting against Imagawa Yoshimoto’s forces.
The Road to Abandonment
There are various theories regarding the time of Moriyama Castle’s abandonment, but the most likely theory is that it occurred after the Battle of Okehazama (1560). As Oda Nobunaga unified Owari Province and expanded his power from Kiyosu Castle, the strategic importance of Moriyama Castle declined.
Another theory suggests that the castle was abandoned around the time of the Honnoji Incident in 1582 (Tensho 10). In any case, by the late Sengoku period, it had lost its function as a castle and disappeared from the stage of history.
Structure and Remains of Moriyama Castle
Castle Structure
Moriyama Castle was a relatively small flatland castle, measuring 58 meters east-west and 51 meters north-south. It is believed to have had a simple structure, surrounded by a single moat and centered around the main keep.
The castle was built on a small hill, offering a view of the surrounding plains. This topographical advantage was a factor in its role as an important military base during the Sengoku period.
The main defensive feature of Moriyama Castle was the dry moat. It is presumed that the castle lacked permanent defensive structures such as stone walls, and instead possessed a typical medieval castle structure centered on earthworks and moats.
Existing Remains
Currently, the Moriyama Castle site is the grounds of Hoshōji Temple. Hoshōji Temple was built to commemorate Matsudaira Kiyoyasu and has a deep connection to the castle site.
The castle site is on a small hill, retaining traces of its former topography. However, only faint traces of dry moats and parts of earthworks can be clearly identified as definite remains. Many remains have been lost due to the passage of time and residential development.
Within the temple grounds, there is a stone monument and explanatory plaque commemorating Matsudaira Kiyoyasu, conveying the historical significance of the site. However, since the grounds are private property, consideration is necessary when visiting.
Value as a Designated Cultural Property
The Moriyama Castle site is recognized as a historical site by Nagoya City and is protected as a regional historical heritage. However, it is not designated as a national or prefectural cultural property, and the state of preservation of the remains is limited.
Nevertheless, it is highly valued for its historical significance as the site of the “Moriyama Collapse,” a crucial event in Sengoku period history, and as a place connected to the roots of Tokugawa Ieyasu.
Highlights of Moriyama Castle | Points to Check on-Site
Hōshōji Temple and Matsudaira Kiyoyasu Memorial Tower
The biggest highlight when visiting the Moriyama Castle ruins is Hōshōji Temple, which stands on the castle site. This temple was built to commemorate Matsudaira Kiyoyasu, and a stone monument in his memory stands on the temple grounds.
Standing before the monument, one can feel the regret of the young warrior who fell before achieving his goals at the young age of 25, and the immense impact his death had on history. The significance of this place in the history of the Matsudaira clan, which produced Tokugawa Ieyasu, the unifier of Japan, is immeasurable.
Topography of the Castle Ruins
The castle ruins, now part of the grounds of Hoshōji Temple, still retain the shape of a small hill. Situated slightly higher than its surroundings, it offers a glimpse into the topographical features of the former castle site.
Walking through the temple grounds and imagining what the warlords of the Sengoku period saw and thought in this place is one of the joys of visiting castle ruins.
Traces of a Dry Moat
With careful observation, faint traces of a dry moat can be seen. While not a clear structure, the subtle undulations of the terrain suggest the presence of a defensive structure.
Knowledge of castle archaeology will allow for a deeper understanding of the remains.
Information Board and Stone Monument
An information board explaining the history of Moriyama Castle is installed at the site. It provides concise information about the circumstances of the “Moriyama Collapse” and the history of the castle.
Learning about the history before your visit will deepen your understanding at the site.
Access and Visiting Guide to Moriyama Castle
Location
- Address: Ichiba, Moriyama-ku, Nagoya City, Aichi Prefecture
- Local Name: Hoshōji Temple Grounds
Access by Public Transportation
By Train and Bus
- Approximately 15 minutes on foot from Obata Station on the Meitetsu Seto Line
- Approximately 5 minutes on foot from the Ichiba bus stop, accessible by bus from Sunadabashi Station on the Nagoya Municipal Subway Meijo Line
While access by public transportation is possible, the location is somewhat inconvenient. We recommend allowing ample time for your visit.
Access by Car
- Approximately 10 minutes from Moriyama Smart IC on the Nagoya Expressway
- Approximately 30 minutes from Nagoya IC on the Tomei Expressway
Parking is available for visitors to Hoshōji Temple, but spaces are limited, so we recommend checking in advance.
Notes for Visitors
Moriyama Castle ruins are located on the private property of Hoshōji Temple. Please note the following points when visiting.
- Be mindful that you are on temple grounds and observe quietly.
- Do not enter restricted areas without permission.
- Always take your trash with you.
- Take photographs within reasonable limits.
- If possible, contact the temple in advance to obtain permission to visit.
Especially for group visits or if you wish to conduct detailed research, it is courteous to contact them in advance.
Estimated Visiting Time
30 minutes to 1 hour is sufficient for visiting the Moriyama Castle ruins themselves. However, if you plan to visit other historical sites in the surrounding area, it is advisable to allocate about half a day.
Best Time to Visit
Since the castle ruins are outdoors, it is recommended to visit in the pleasant weather of spring (March to May) or autumn (September to November). In mid-summer, there is little shade, so precautions against heatstroke are necessary.
Historical Sites Around Moriyama Castle
Nagoya Castle
Nagoya Castle, located about 30 minutes by car from Moriyama Castle, is known as the residence of the Owari Tokugawa family, one of the three main branches of the Tokugawa clan. Although from a different era than Moriyama Castle, you can feel the history of the same Owari Province.
Nagoya Castle Ruins
The site of Nagoya Castle, to which Oda Nobumitsu moved from Moriyama Castle, is believed to have been located within the grounds of the current Nagoya Castle. Known as the birthplace of Oda Nobunaga, it offers a historical connection to Moriyama Castle.
Kiyosu Castle
Kiyosu Castle, Oda Nobunaga’s base, is about a 40-minute drive from Moriyama Castle. A reconstructed keep now stands, making it an important spot for understanding Owari during the Sengoku period.
Komakiyama Castle
Komakiyama Castle, built by Oda Nobunaga, is also located within Owari Province, just like Moriyama Castle. It offers insights into the characteristics of Nobunaga’s castle architecture, and comparing it to medieval castles like Moriyama Castle would be interesting.
Differences between Moriyama Castle and Other Moriyama Castles
There are several castles named “Moriyama Castle” in Japan. To avoid confusion, let’s clarify the main Moriyama Castles. ### Etchu Moriyama Castle (Takaoka City, Toyama Prefecture)
Moriyama Castle, located in Takaoka City, Toyama Prefecture, is a mountain castle counted as one of the “Three Great Mountain Castles of Etchu,” alongside Matsukura Castle and Masuyama Castle. During the Sengoku period, it was the residence of the Jinbo clan, and later became the residence of Maeda Toshinaga.
The site of the main keep is a designated historical site of Takaoka City, and it is a completely different castle from Owari Moriyama Castle. Although the scale and history differ, the shared name “Moriyama Castle” requires caution when searching.
Omi Moriyama Castle (Moriyama City, Shiga Prefecture)
It is believed that a Moriyama Castle also existed in Moriyama City, Shiga Prefecture. It is thought to have been built by the Sasaki Rokkaku clan and was active during the Tenbun era (1532-1555), but many details remain unknown.
To distinguish it from other Moriyama Castles, the Moriyama Castle discussed in this article may be referred to as “Owari Moriyama Castle” or “Moriyama Castle (Owari Province).”
Historical Significance of Moriyama Castle
Connection to the Roots of Tokugawa Ieyasu
The greatest historical significance of Moriyama Castle lies in the fact that it is the place where Tokugawa Ieyasu’s grandfather, Matsudaira Kiyoyasu, lost his life in the “Moriyama Collapse.”
If Kiyoyasu had not been killed at that time and had succeeded in his invasion of Owari, the Matsudaira clan might have become a powerful force much earlier, and the course of the Sengoku period could have been significantly different. Kiyoyasu’s death led to a temporary decline of the Matsudaira clan, and his grandson, Ieyasu, faced hardship as a hostage of the Imagawa and Oda clans during his childhood.
This experience of hardship is believed to have greatly influenced Ieyasu’s character development and political skills. In that sense, Moriyama Castle can be considered the starting point of the 260-year history of the Tokugawa Shogunate.
A Symbol of Gekokujo in the Sengoku Period
The “Moriyama Collapse” is a classic example of gekokujo, where a vassal murdered his lord. It is considered historically significant as an event symbolizing the characteristics of the Sengoku period.
However, whether this incident was a simple case of gekokujo or whether there was a conspiracy by the Oda clan behind it remains a subject of ongoing debate. It continues to attract the attention of many researchers and history enthusiasts as a historical mystery.
Its Place in the Process of Unifying Owari
Moriyama Castle was one of the important bases in the process of unifying Owari by Oda Nobuhide and his son Nobunaga. The Oda clan served as the castle lords and it functioned as a center of control for the surrounding region.
As Oda Nobunaga unified Owari and began his path to unifying Japan, smaller base castles like Moriyama Castle gradually lost their role. In that sense, the history of Moriyama Castle can be seen as an example of the transformation of castles during the transition from the medieval to the early modern period.
Current Status of Research and Preservation of Moriyama Castle
Archaeological Survey
No large-scale archaeological excavations have been conducted at the Moriyama Castle site. This is primarily due to the site being privately owned and the ongoing residential development.
Therefore, detailed information about the castle’s structure and history must rely on historical documents and estimations based on topographical observations. If an excavation is conducted in the future, new historical facts may be revealed.
Preservation Challenges
There are several challenges in preserving the Moriyama Castle site.
Firstly, because it is privately owned, public preservation and maintenance are difficult. While the current state is maintained thanks to the generosity of Hoshōji Temple, there are uncertainties regarding future preservation.
Secondly, the historical environment of the castle site is changing due to surrounding urbanization. The former landscape has changed significantly, making it difficult to imagine the topography and environment at the time the castle was built.
Thirdly, the state of preservation of the remains is not good. Due to the scarcity of clear remains, it is difficult for general visitors to truly grasp the significance of the castle ruins.
Future Prospects
Considering the historical value of Moriyama Castle ruins, more proactive preservation and utilization are desirable. For example, the following initiatives could be considered:
- Creation of a detailed layout map based on a thorough survey
- Improvement of explanatory and informational boards
- Restoration of the castle’s appearance using digital technology
- Utilization for local history education
- Holding historical events based on the “Moriyama Collapse”
These initiatives would allow us to convey the historical value of Moriyama Castle to a wider audience.
Reference Materials for Learning About Moriyama Castle
Basic Literature
The following are basic literatures for learning about Moriyama Castle:
- “Comprehensive Survey of Japanese Castles,” Volume 9 (Shin Jinbutsu Oraisha)
- “History of Aichi Prefecture” (Yamakawa Publishing)
- “History of Nagoya City”
- “History of Moriyama Ward”
These documents provide detailed descriptions of the history of Moriyama Castle and the “Moriyama Collapse.”
Research on Matsudaira Kiyoyasu and the Moriyama Collapse
There are many studies on the “Moriyama Collapse” and its historical impact.
- *The Matsudaira Clan of Mikawa* (Shin Jinbutsu Oraisha)
- *The Birth of Tokugawa Ieyasu* (Yoshikawa Kobunkan)
- Various Sengoku period history research books
These research books provide detailed analyses of the impact the Moriyama Collapse had on the Matsudaira clan and Tokugawa Ieyasu.
Internet Resources
In modern times, information about Moriyama Castle can also be obtained online.
- Castle information websites such as Kojodan
- Nagoya City official website
- Various history blogs and research sites
However, since the reliability of internet information varies, it is recommended to refer to multiple sources and, if possible, verify with specialized books.
Summary | Moriyama Castle Tells the Story of Sengoku History
Moriyama Castle, though small in scale, is a castle of extremely important significance in the history of Japan’s Sengoku period.
The Moriyama Collapse of 1535 claimed the life of Matsudaira Kiyoyasu, a young hero, thwarted the Matsudaira clan’s expansion, and ultimately contributed to the turbulent life of Tokugawa Ieyasu. Had this incident not occurred, the course of history from the Sengoku period to the Edo period might have been drastically different.
The current site of Moriyama Castle quietly preserves its history as the grounds of Hoshōji Temple. While there are few clearly visible remains, standing here, one can feel the transience of the Sengoku period and the weight of this pivotal moment in history.
Despite being located in the urban area of Nagoya, Moriyama Castle remains a valuable historical site where one can feel the spirit of the Sengoku period, and it should be carefully preserved for the future. Moriyama Castle is an indispensable and important destination for anyone tracing the roots of Tokugawa Ieyasu or learning about the Sengoku history of Owari Province.
Castle enthusiasts, those interested in Sengoku history, and those interested in Tokugawa Ieyasu should definitely visit this historical site. You’re sure to be moved by the grand historical story told by these small castle ruins.
