Iida Castle (Azumi)

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AdzumiIidajou (2).jpg


Iidajō was the castle of the Obinata Clan who were vassals of the Nishina Clan. Iidajō was constructed in the early-to-mid' 16th century, and it is thought that the Nishina Clan mobilised various clans and people to construct Iidajō and surrounding fortresses as the threat from the Uesugi and Takeda clans grew.

Iidajō was captured in 1556 by Yamagata Masakage, a commander of the Takeda forces. It is believed that Takeda forces then used Iidajō was a base for pushing into northern Aźumi, toward Uesugi territory in Niigata, though it is not known when the castle was decommissioned.

Visit Notes

Iidajō is a yamajiro (mountaintop castle) ruin in Kamishiro Township, Hakuba Municipality. It is the main site in a network of forts on the Tsukiyodana tableland sometimes referred to collectively as Tsukiyodanajō. Iidajō is also called Tsukiyozawajō. Ruins feature kuruwa (baileys), dorui (earthen ramparts), koguchi (gate complex) ruins, and various trenches. Fair warning: much of the ruins are overgrown and difficult to explore.

Iidajō's layout is quite interesting, and expansive, with three bailey complexes. I approached from the south, which brings one to the lower, second bailey complex. It is protected by two long, stacked yokobori (horizontal trenches), one overlooking the other. This configuration is not so common in Shinano, but was built because there is a wide hollow or 'saddle' in the mountain below, rather than a narrow ridge. I followed these trenches along and came to a gate ruin with embankments which formed the entrance to the second bailey. The second bailey is slightly terraced rather than a single continuous flattened space.

Between the lower second bailey and upper first bailey is another yokobori, though now it is quite shallow, being filled in with falling detritus from the mountain. The first bailey complex is itself made up of multiple baileys. Narrow baileys along the ridge have dorui banked up to the north. There is some terracing overlooking a cliff to the east but it was far too overgrown to see properly. Between the narrower easterly baileys and the main bailey of the upper complex are a set of double horikiri (trenches which bisect the ridge). Essentially together they form a 'W'-shape along the ridge, and this was the most impressive feature of the site for me (and thankfully not so overgrown!). Above is the main bailey which has also a rear trench-embankment system.

A third, small bailey complex can be found in the valley between the two larger bailey clusters. This is a valley bailey with proportions almost like a wier and reservoir, except the embankment which would otherwise dam the valley has in the centre a large opening where a gate would've stood. This was the original way up to the castle. Having come down this far, I decided I'd exit the mountain this way despite warnings from some other castle-explorers about doing so - though they did. I was able to follow a nice stream down toward rocky rapids (called 'Dog River'). Maps showed an old foot bridge - in a very dubious state now - and I had to fight through grasping vines to get to this final portal from the mountain, but once I did I was home-free, coming to an old dirt track which led back to civilisation. It was along here, in a mostly emptied reservoir, I also encountered a troupe of monkeys.

I encountered a bear at this castle site; in the second bailey, infact. I heard a plodding through the undergrowth and waited to see what was coming toward me. As I have said, this site is very overgrown, so it's difficult to see for any distance ahead. When I saw through the trees jet black fur, along with an ambling locomotion of heavy footfalls, I thought it must be a bear. Part of me wanted to stay quiet so as to get a better look, but a more sensible part triumphed, and, seeing the beast was already quite close enough, I gave a cautious shout of "Oi!". The creature stopped. Louder and quicker this time I shouted "Oi, Oi, Oi!", and the animal went into a quick retreat. I heard it scamper off down the mountainside and, grabbing a large stick, went to the edge of the bailey to try to see it again. I didn't glimpse anything thereafter, but listened to the rustling of the thing's retreat for about half a minute as it bolted away down the mountain.

Upon reflection, we must've been coming up to the bailey at the same time, winding our way toward each other. Since I acted quickly, the time between my seeing the animal and the encounter ending was very short, and I didn't see its face, but with certainty in the moment it was a black bear. From its fur and the way it plodded I think it couldn't've been anything other. Only, and thankfully, it didn't seem very big, but there was some distance, I'd say 10m so as not to underestimate though it felt shorter, and there was a slight slope to account for on which I was above. I've always figured that most bears in the wild aren't so large, and many candid pictures showing them in Japan's forests seem to demonstrate that. The wild bears are often malnourished, half starved, perhaps diseased, and their growth is stunted. It's also likely I encountered a juvenile. I had a good look at a juvenile bear before as it climbed a tree, and at that time I remember thinking that though the body was not much larger than the average dog's, the head was very large. This time I was aware of the bear before it was aware of me - or maybe it was curious on a scent and didn't realise it was approaching a human - but I am now reminded of another not dissimilar mystery encounter I had when, again at an overgrown, lonesome castle site (Minami-Hirasejō), I crashed through the bushes and disturbed something that felt very large as it moved to flee; though I didn't see it at all, and upon investigation found a wide bed of flattened grass. But at that time I thought it might've been a boar, since they can be very big too. Next I'll encounter Hibagon, I'm sure.

I mentioned I exited Iidajō via a creek. To get to this point one must go quite high up via the river valley first. In other words, except by this almost spiralling route, it is not advisable to climb to this site from directly below, as the fort is naturally protected by steep terrain and cliffs in the north and east. My point of entry was actually to come from the south via the mountain. Some castle-explorers recommend this route, though not all of them have actually taken it themselves. Looking at a topographic map, the terrain in the tableland area seems gentle or flat, almost inviting, but between Iidajō and its satellite fortification, Akiba-toride, the mountain is horrendously overgrown without trails. I had to crawl on hands and knees along gametrails under bushes. At one point along the ridge, a landslide-eaten drop on one side and a wall of skinny trees on the other, I commando-crawled, and, when the ridge dropped, I slithered down about 40m as though having a wonderful time on a water slide! It was during this tumult that my bear bell, which I tried to keep an eye on, broke and was lost. Just fifteen minutes later and I had my encounter of the furry kind. This has made me a believer in the power of bells.

Note: this site is Iidajō in historical Aźumi County, not to be confused with Iidajō in historical Ina County, both in Shinano Province (Nagano Prefecture).

  • Double trenches

Castle Profile
English Name Iida Castle (Azumi)
Japanese Name 安曇飯田城
Alternate Names Tsukiyozawajō (月夜沢城)
Founder Obinata Clan
Year Founded Early-to-mid' 16th century
Castle Type Mountaintop
Castle Condition Ruins only
Historical Period Pre Edo Period
Artifacts Yokobori, Horikiri, Kuruwa, Dorui, &c.
Features trenches
Visitor Information
Access 30+min hike from Akiba-toride via the 1,013m peak, heading north
Visitor Information 24/7 free; mountain
Time Required 60 minutes
Location Hakuba, Nagano Prefecture
Coordinates 36° 39' 30.38" N, 137° 49' 59.59" E
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Added to Jcastle 2023
Contributor ART
Admin Year Visited Viewer Contributed
Friends of JCastle
Jōkaku Hōrōki

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