Yamanaka Castle (Mikawa)

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Mikawa Yamanaka Castle, one of the largest mountain castles in Aichi Prefecture, is said to have been built around 1500 by the Saigo clan, vice-governors of Mikawa Province.

Yamanaka Castle is said to have been built as the clan’s emergency fortress, but given its large size and location, it could well have been the headquarters and residence of the Saigo family.

In the early mid 15th century, the Saigo clan advanced northwards across the Otogawa River where they established Okazaki Castle. However, this move brought them into conflict with Tokugawa Ieyasu's grandfather, Matsudaira Kiyoyasu, then 19 years old and leader of the Matsudaira family for six years. Kiyoyasu was able to defeat the Saigo, and take Okazaki Castle as his own.

After Kiyoyasu was murdered in a mishap at Moriyama Castle in 1535, Yamanaka Castle became the headquarters for the Imagawa clans’invasion of western Mikawa.

During the Battle of Azukizaka, fought between Imagawa Yoshimoto and Oda Nobuhide in 1548, Yamanaka Castle and the nearby Oka Castle became important bases for the Imagawa forces. In 1560, after the defeat of Imagawa Yoshimoto at the Battle of Okehazama, Tokugawa Ieyasu attacked Yamanaka Castle, returning it to the possession of the Matsudaira / Tokugawa. From 1564 onwards, Ieyasu’s close and trusted vassal, SakaiTadatsugu, took command of Yamanaka Castle. Yamanaka Castle was abandoned in 1590 when Ieyasu moved to the Kanto region.

Visit Notes

The total area of Yamanaka Castle covers about 400 metres east west and 200 metres north south on a 120 metres high mountain, surrounded by two streams which form a natural moat. The Honguruwa (main compound) is about 30 metres long and 15 metres wide, with Ni-no-maru area, about 50 metres long and 20 metres wide, built at about a meters height difference. These baileys are surrounded by thick dorui earthen walls. These earthworks have been eroded somewhat over time and in the past would have been much higher and more prominent.

To the east and below the main and second baileys is the 20-metre-long square shaped Higashi-guruwa bailey, which is key to the castle’s central defences. Below it, on two ridges stretching to the north and east, are terraces of baileys. Each line of terraces has dry moats at the choke points and twisting paths to form enemy obstacles on approach.

Just below this eastern bailey is a semi-circular Umadashi! Umadashi were an effective defensive barrier and compound complex built in front of castle gates, used as a screen to facilitate cavalry charges and attacks during times of siege. Like a barbican gate system, the Umadashi worked like an airlock for a castle, allowing attack parties to sally forth and safely return, without letting the enemy in.

They served as a first line of defense, protecting the main gates. It’s only a small Umadashi, but to see it used in such a position, and so high up the mountain was fascinating!

Yamanaka Castle’s multiple (at least 8!) northern facing tatebori, vertical trenches up the side of the mountain, and horikiri, deep V shaped trenches preventing enemy advances across mountain ridges, (lost count of how many) are quite impressive.

Like most yamajiro, Yamanaka Castle makes very good use of the natural defences of the mountain, augmented and strengthened by the ingenuity of the samurai and their earthwork skills. Naturally, the top of the mountain was cut flat to form a circle.

Parts of the mountainside are also cut away to form Obi-kuruwa, like flat paths around the mountainside. These were created not only to create more space, but also to make the hillside steeper and more difficult to climb. These steep slopes, called a kirigishi, are a most important defensive feature. Most people only see the obi-kuruwa baileys without realising that they are the result of a kirigishi being formed. At Yamanaka Castle, the easily recognisable Obi-kuruwa are very visible. Walking around the narrow ring like paths, you can see how difficult it would be to climb up the bank and how easy it would to shoot arrows and matchlocks in defense from above.

Yamanaka Castle has played an important role in history and boasts links with the Matsudaira, Tokugawa, Imagawa and Sakai clans. It is easily accessed, relatively easy to climb, is being maintained slowly but surely, and being the largest mountain castle site in Aichi Prefecture, it’s a must-see.

Profile by Chris Glenn (edited by ART).

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  • Main Bailey
  • Dorui
  • Main Bailey Complex From Below
  • Belt Bailey beneath Main Bailey - Obikuruwa
  • Umadashi (Barbican)
  • Higashi Kuruwa / Eastern Bailey
  • Two tiers of obikuruwa beneath Second Bailey
  • Castle Mount
  • Second Bailey
  • First Bailey
  • Horikiri (Trench)
  • Ohhorikiri / "Big Trench"
  • Horikiri / Trench in profile
  • Castle Layout Map (Nawabari)
  • Honkuruwa / Main Bailey
  • Obikuruwa and Kirigishi
  • Fourth Bailey looking across trenches to second

Castle Profile
English Name Mikawa Yamanaka Castle
Japanese Name 三河山中城
Founder Saigo Clan
Year Founded c. 1500
Castle Type Mountaintop
Castle Condition Ruins only
Designations Local Historic Site
Historical Period Pre Edo Period
Artifacts Horikiri, Tatebori, Kuruwa, Dorui, Obikuruwa
Features trenches
Visitor Information
Access Meiden-Yamanaka Station on the Meitetsu-Nagoya Line; 15 minute walk
Visitor Information 24/7 free; mountain
Time Required 1hr+
Location Okazaki, Aichi Prefecture
Coordinates 34° 53' 44.48" N, 137° 13' 47.35" E
Loading map...
Added to Jcastle 2022
Contributor 豪谷
Admin Year Visited Viewer Contributed
Friends of JCastle
Jōkaku Hōrōki

(one vote)
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13 months ago
Score 1++

Yamanaka Castle is an earthworks fortification ruin situated on a hill between the Maigi and Haguri townships in Okazaki Municipality. Chris Glenn introduced this site to our group, citing it as one of the largest mountaintop castle sites in Aichi Prefecture. It’s nowhere near in scale to large sites I’ve visited in Nagano, such as Haibara or Kibune castles (the latter is virtually unknown), or Niigata, such as Kasugayama (well known) or Nechi (not so well known) castles, and it only took me about an hour to see everything, but it does have many interesting features and the earthwork ruins are well preserved. The best thing about this site is that it is well maintained throughout. The ruins can be seen clearly without trees and other flora obscuring, allowing its structure and layout to be readily appreciated. It is a rare treat in this regard, and, going around the whole site, I found only one section of the castle to be somewhat overgrown.

Features of the site include baileys (kuruwa, koshiguruwa, &c.), trenches (horikiri, tatebori, &c.), and earthen ramparts (dorui, kirigishi, &c.). An interesting feature of the site is a small umadashi (barbican, which aren’t usually found at such elevated sites. The layout of the castle is concentrated around three main bailey groups with northerly spurs following the ridges from each. The main bailey complex is located to the west and is embossed to the northwest with several tiers of terraced koshiguruwa (sub-baileys).

The castle’s western, northwestern and central northern spurs all terminated in well-constructed horikiri (trenches which bisect the ridgeline), which I was very happy with. In several spots, but particularly along the inside of the ‘U’-shape formed between these two latter ridges, are several tatebori (climbing trenches). In medieval mountaintop castle warfare, horikiri made approaching along a ridgeline hazardous, and tatebori impeded later troop movement along mountainsides, and so the two features are highly complementary.


14 months ago
Score 1++
It’s good to see this castle profile up on JCastle. Thanks for putting this up. Now I can see what I have missed by opting to go to Ganryakuji Castle instead. I had only enough time and daylight to visit one of them after visiting some other castles on the same day, so I chose Ganryukuji Castle because Yamanaka Castle had looked more overgrown based on photos that I saw back in 2015. Ganryukuji Castle is located on the same Meiden railway line as Yamanaka Castle, just a few train stations away. I will have to suss out Yamanaka Castle whenever I next go “castle-hunting” in the Okazaki-Toyohashi area.