Chausuyama Castle (Nukata)




Chausuyamajō's date of construction is unknown, but was likely built by the Kira Clan, and is thought to have been used as a satellite fortification and further redoubt of Tōjōjō in the foothills. Chausuyamajō also functioned as an important signal tower for the Matsudaira Clan, as its smoke signals could be seen from both the Chita and Atsumi peninsulae which hem in Mikawa Bay. Castellans included Ôdaka Danjō, Ôkura Danjō, and Matsudaira Yazaemon.

Visit Notes

Chausuyamajō is a yamajiro (mountaintop castle) ruin on the border of Sumi village, Kōta Township in Nukata County, and Kira Township in Nishio Municipality. The ruins feature earthworks such as kuruwa (baileys), koshikuruwa (terraced baileys), karabori (dry moat), dobashi (earthen bridge), dorui (earthen ramparts) and perhaps a tatebori (climbing trench). There is also some ishigaki (stone-piled retaining walls), but this appears to have been built for a temple which occupied the castle-mount in later times.

The main bailey is surrounded by the remains of dorui, and, below, a ring bailey. Parts of the ring bailey, particularly to the south where there is another terraced bailey, look like they also had dorui piled up there. There is a depressed bailey in the east where there is a 'saddle' in the ridge, and beyond that there is a tertiary bailey protected by a dry moat complex with a deformed dobashi. This outer bailey has dorui around the western edges. Beneath the western bailey, though it was not shown on the map I was using, there is another koshikuruwa on the northern side.

The outer, tertiary bailey has a nice moat complex toward the main bailey, as mentioned, but not, oddly enough, to the rear. The rear of this outer bailey appears to be undeveloped, and this is somewhat mysterious as it would appear to constitute a major breach in the fort's integral defence. Either construction was not completed here or, as I figured, landslides have effaced the footprint of the fortress here.

On a small peak above the rest of the castle-mount it is said there was a noroshidai (tower or kiln for smoke signals). The map I had showed a tatebori just beneath here on the approach from the fort proper. I identified this excavation but it's very short and doesn't go down very far; the terrain beneath is gently sloping, so maybe this was also the result of landslides or natural degradation.

Although not well known as a castle ruin, Chausuyama is popular with hikers, and the trails are easy to walk. I came from a trail to the south, just a little way down from the quarry. The entrance to the trail is well hidden with only a break in the bushes along the roadside as a tell, but once one steps into the forest the trails become clear; take the trail going left. This trail goes by a kofun (ancient burial mound) which has the stone vaulting removed and the burial chamber exposed. It then proceeds up to the castle ruins via a path between the quarry and a bamboo grove. The route is quite scenic and there are good views throughout of the surrounding countryside and Mikawa Bay.

This site is Chausuyamajō in Nukata County, not to be confused with Chausuyamajō in Toyota Municipality (historical Kamo County), or Chausyamajō in Shinshiro Municipality (historic Shitara County), all in Mikawa Province and Aichi Prefecture.


Castle Profile
English Name Chausuyama Castle (Nukata)
Japanese Name 額田茶臼山城
Founder Kira Clan
Year Founded Unknown
Castle Type Mountaintop
Castle Condition Ruins only
Historical Period Pre Edo Period
Artifacts Horikiri, Kuruwa, Dorui, Dobashi, &c.
Features trenches, stone walls
Visitor Information
Access I cycled from downtown Okazaki along the Okazaki-Hekinan Road
Visitor Information 24/7 free; mountain
Time Required 60 minutes
Location Kōta, Aichi Prefecture
Coordinates 34° 50' 20.62" N, 137° 7' 4.51" E
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Added to Jcastle 2024
Contributor ART
Admin Year Visited Viewer Contributed
Friends of JCastle
Jōkaku Shashin Kiroku
Jōshi Meguri Bibōroku
Shiro Rekishi Meguri

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