Iotojō was built as a fortified signal tower by Inukai Hanzaemon, a vassal of the Ogasawara Clan, who were hegemonic in Shinano at that time (early 16th century). The fort is mentioned as having played a role in the battle of Shiojiri Pass, which is located to the south, in 1548. The Shiojiri Pass is a strategic area at the site of a bottle neck between the counties of Suwa and Ina. Ogasawara forces were defeated at the pass by Takeda Shingen, and the battle there is said to have demonstrated the superlative cavalry tactics of Takeda forces. There is some indication that Iotojō was intended to be expanded but construction was halted, perhaps because of the Ogasawara defeat at the pass, or because the fort was located too far from the pass to effectively control it.
Iotojō is a wild yamajiro (mountaintop castle) in a relatively remote corner of Shiojiri Municipality. The road to the castle is very steep, and the trail starts next to a bridge where the road is closed. It’s quite a challenge to climb to this fort ruin. It is steep and there are rope sections (one of which I repaired; I’m no boy scout but I know I did a good job with the knot because it didn’t give when I later used it to descend!).
The fort is a single bailey complex fort with terracing to the front and rear (a single lip to the immediate rear). The main bailey is partially divided by terracing, leaving an uneven terrain. There is a hokora (mini-shrine) in the main bailey now. The sides of the bailey are very steep. To the rear is a ridge which has been collapsed by landslides so that now it is more like a climbing frame of tree roots than it is solid ground. If one goes over this ridge, on which the soil is so loose it sinks beneath one’s feet, one will come to a gnarly rockface with an ancient rope going up it. Climbing this uninviting path, trusting in a dubious rope, is no mean feat, but on the more intact portion of the ridge above is a series of terraced baileys ending in a horikiri (trench). This site is fairly dangerous to master.
|English Name||Ioto Castle|
|Year Founded||Early 16th Century|
|Castle Condition||Ruins only|
|Historical Period||Pre Edo Period|
|Access||Nearest Station is Midoriko on the Chūō Line|
|Visitor Information||24/7 free; mountain|
|Time Required||60 minutes|
|Location||Shiojiri, Nagano Prefecture|
|Coordinates||36° 6' 42.41" N, 138° 1' 13.44" E|
|Added to Jcastle||2022|
|Admin Year Visited||Viewer Contributed|
|Friends of JCastle|