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Castle Kanayama Castle

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Kanayama Castle (金山城) is a hilltop castle located on Mount Kanayama, a 200-metre tall hill in modern-day Ōta City, Gunma Prefecture. The castle is strategically located in the plain between the Tone River and the Watarase River. It is a National Historic Site.

Kanayama Castle (Gunma) 01

Kanayama Castle (Gunma) 02

Based on the Aerial Photograph Searching Service of the Geospatial Information Authority of Japan. The location of the enclosures is estimated.


According to the diary of the court noble Fujiwara no Munetada, Mount Asama erupted in August 1108 and destroyed the area around Mount Kanayama. Minamoto no Yoshishige (源義重, 1135–1202), a progenitor of the Nitta branch of the Minamoto, tried to revive that area and founded Nitta Manor (新田荘 Nitta-sō). In the late Kamakura period, Nitta Yoshisada (新田義貞, 1301-1338), who was instrumental in defeating the Kamakura shogunate, raised a local army. Later, Yoshisada committed seppuku in a battle against an ally of Ashikaga Takauji. The Iwamatsu branch of the Nitta clan became lords of Kanayama. Iwamatsu Iezumi (岩松家純, 1404-1469) constructed Kanayama Castle in 1469.

In 1528, in what would be known as the Kyōroku Incident (享禄の変), the Yokose (横瀬), retainers of the Iwamatsu who later changed their name to Yura (由良) overthrew the Iwamatsu and expanded their land holdings in Kōzuke Province (上野国, modern-day Gunma). They seized the castles in Kiryū, Ashikaga and Tatebayashi, and reinforced Kanayama Castle. In the Sengoku era, Kōzuke Province was fiercely contested among the Hōjō of Sagami Province, the Uesugi of Echigo Province and the Takeda of Kai Province. The Yura first sided with Uesugi Kenshin, but in 1566 pledged allegiance to the Hōjō. In 1574, on the order of Kenshin, the Satake clan (佐竹氏) attacked and besieged Kanayana Castle. In 1580, Takeda Katsuyori (武田勝頼, 1546-1582), and in 1583, Satake Yoshishige (佐竹義重, 1547-1612) attacked the castle again, but it was never taken.

In 1584, Yura Kunishige (由良国繁) and his brother Nagao Akinaga (長尾顕長) were taken prisoner by the Hōjō during a respectful visit at Odawara Castle and asked to surrender. However, Kunishige's mother, Akai Teruko (赤井輝子, 1514-1594), also known as Myoin-ni (妙印尼), allied with the Satake and the Sano and resisted the Hōjō with a remaining army of some 3,000 troops for 15 months. She surrendered Kanayama Castle under the condition that her two sons were released. Kunishige moved to Kiryū Castle (桐生城), and Kanayama was seized by the Hōjō.

The Hōjō would hold the castle only for a few years. During Toyotomi Hideyoshi's Odawara campaign in 1590, Maeda Toshiie (前田利家, 1538-1599) captured Kanayama Castle which was later abandoned. Kunishige was still detained at Odawara Castle when Myoin-ni led an army to support Hideyoshi. After the war, Kunishige was made lord of Ushiku (牛久, in present-day Ibaraki Prefecture) in light of his mother's achievements. Had Myouin-ni been the head of the family, she would have made a daimyō of great standing.

Visiting the castle:

I collected information about the castle at the visitor centre of the castle at the foot of the hill near the main entrance. The enormous castle site covers almost the entire hill. In particular, the West castle and the ninomaru (二ノ丸) are worth visiting. I went there by car, but visitors can start climbing from the visitor centre.

Kanayama Castle (Gunma) 03

West Castle (西城 Saijō)
There is a parking lot near Saijō. I started out towards the honmaru (本丸, inner enclosure) from there.

Kanayama Castle (Gunma) 04

West Turret (西矢倉台 Nishiyagura-dai)
A trench (堀切 horikiri) on the west side of the castle. The bottom of the horikiri is a stone-paved passage.

Kanayama Castle (Gunma) 05

This is another trench.

Kanayama Castle (Gunma) 06

Watchtower (物見台 Monomi-dai)
This is an entrance to the monomi-dai. There is a stone pile at the front of the passage designed to hide the end of the passage from view.

Kanayama Castle (Gunma) 07

There are two sentries on the watchtower.

Kanayama Castle (Gunma) 08

The view of Mount Akagi (赤城山) from the watchtower.

Kanayama Castle (Gunma) 09

Baba enclosure (馬場曲輪 Baba Kuruwa)
This was a sort of staging area for the guards protecting the koguchi.

Kanayama Castle (Gunma) 10

Lunar Pond (月ノ池 Tsuki-no-ike)
Water is filled in the round pond surrounded by a stone wall. It looked awe-inspiring!

Kanayama Castle (Gunma) 11

Main Entrance (大手虎口 Ōtekoguchi)
The passage to the main castle was heavily defended. During the Sengoku period , it was thought that stone walls were not used in mountain castles in the Kantō region, but the excavations at Kanayama Castle proved this to b wrong. The castle has a sophisticated stone wall with drainage channels.

Kanayama Castle (Gunma) 12

Remains of stone paving and of a kamado 竈, (oven), and the kitchen facility was reconstructed.

Kanayama Castle (Gunma) 13

Third enclosure (三ノ丸 sannomaru)
The stepped stone wall has been beautifully restored.

Kanayama Castle (Gunma) 14

Solar Pond (日ノ池 Hi-no-ike)
This is another circular pond. It is thought to have been used for ceremonies such as praying for victory and for rain.

Kanayama Castle (Gunma) 15

Second enclosure (二ノ丸 Ninomaru)
On the left side is the stairs to the Honmaru.

Kanayama Castle (Gunma) 16

Main enclosure (本丸 Honmaru)
Nitta Shrine (新田神社) is located at the site of the Honmaru.

Kanayama Castle (Gunma) 17

An excavation in progress.

Kanayama Castle (Gunma) 18

Date of visit: 24 November 2013


  • Address: 40-106 Kanayamacho, Ōta, Gunma 373-0027
  • Access: 4 kilometres from Tobu Isesaki Line Ōta station
    4 kilometres from Kita-Kantō Expressway Ōta-Kiryu Interchange via National Route 122
  • Parking: Next to West castle, or in the guidance centre (see spot 'P' pointed on the above map)
  • Other sights: Koizumi Castle
Next article in the series 'Walking the Japanese Castles': Shinagawa Battery (Odaiba)
Previous article in the series 'Walking the Japanese Castles': Koizumi Castle
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Hiroto Uehara
Hiroto is an ordinary Japanese office worker, but his true mission is searching for castles on the weekend.


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Hiroto Uehara
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〒373-0027 群馬県太田市金山町40−106

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