Kanjōsan Castle, Medieval mountain fortress in Aioi, Japan
Kanjosan Castle is a medieval mountain fortress built on narrow terraces at roughly 250 meters elevation along the hillside. Its stone walls are distributed across different levels, with the central area originally measuring about 40 by 20 meters.
The fortress was originally established by the Uryu clan during the Kamakura period and later came under the control of the Akamatsu clan, who used it as a strategic stronghold. In the 14th century, it became central to conflicts with imperial forces reshaping the political landscape.
The name Kanjosan reflects how the Akamatsu clan was honored for their military achievements, translating to 'mountain of citation'. Walking through the ruins, you can sense the importance this place held in the region's past.
Visitors reach the ruins via hiking trails that start from a nearby parking area. It is best to wear sturdy footwear and allow time for the climb, as the paths are steep and sometimes unpaved in places.
The fortress withstood a lengthy siege lasting about 50 days by forces under Nitta Yoshisada during the political upheaval of the 14th century. This stubborn resistance made it a symbol of resilience during that turbulent period.
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