Sunday, April 26, 2020

Tenjinyama Castle (Musashi) -Change of role and structure-

Tenjinyama Castle (Musashi)

-Change of role and structure-



Name: Tenjinyama castle (Tenjinyama-jo)
Place: Iwata Nagatoro town, Saitama
Type: Mountain Castle
Built: 15th century?
Remaining remnants: Stone walls, clay walls and moats 

Brief History

Tenjinyama castle (天神山城) is located over Tenjin-yama mountain, one of 100 meter height from hillside at the side of Ara-kawa river in Nagatoro town. Nagatoro area is a narrow valley at the upstream of Ara-kawa river, which prolongs about 4 kilometer and with ravines at both edge. Castle site exists north edge of this Nagatoro valley.

Nagatoro area is a curving point of Arakawa river which flows from southward turns to eastward, and also the exit point from Chichibu hills to Kanto plain. In addition to the role of control point of Chichibu-Oukan road which connects Musashi province (Saitama prefecture) and Kai province (Yamanashi prefecture) passing Karisaka-Toge pass, this area is a diverging point to the road to Kozuke province (Gunma prefecture) across Mase-Toge pass.

Origin of Fujita clan

Precise year is unknown but Tenjinyama castle was used as a main base of Fujita clan, a traditional local lord which originally held current Yorii area. Fujita clan was originally a branch family of Inomata clans, a group of local samurais originally came from the central noble of Kyoto city.

Fujita clan activated at the establishment of Kamakura Shogunate and grew as a major local lord of Musashi province. After the fall of Kamakura Shogunate, among the conflict between the South Court and Muromachi Shogunate, Fujita clan could survive probably dividing their family to both side.

At the same time, Chichibu basin was originally held by Shiratori clan or Iwata clan, which belonged to Tanto clan, which was another group of local lords. As there was Shiratori Shrine at the side of the mountain, Tenjinyama castle might be built by Shiratori clan at first.

Growth of Fujita clan

Among the conflict between Muromachi Shogunate and the South Court, local lords of Tanto clans belonged to the South Court side and finally fell. Muromachi Shogunate overwhelmed the South Court sent their representative Kamakura Kubo Highness and its minister Kanto-Kanrei, and reorganized local lords of Kanto region under them.

At this time Fujita clan extended their territory to Chichibu basin, and became one of major retainer of Kamakura Kubo along with Oishi clan, which held current Hachioji area at the side of Tama-gawa river. Both of Fujita clan and Oishi clan grew their power by controlling river control and production of woods from backward mountains.

In the latter half of 15th century, severe internal conflicts occurred at Kanto region between Kamakura Kubo Highness and Uesugi clan which served Kanto-Kanrei, and next Yamanouchi Uesugi clan and Ogigayatsu Uesugi clan which were main family and branch family of Uesugi clan.

As Yamanouchi Uesugi clan resided at Hirai castle just 15 kilometer northwest of Tenjinyama castle, Fujita clan belonged to Uesugi clan and worked at its military activity. Finally both Uesugi clan agreed in the beginning of 16th century, but utilizing this confusion Hojo clan expanded their territory from westward of Kanto region.

Take over by Hojo clan

In 1546, Hojo clan which seized south part of Musashi province including Edo castle (Tokyo Metropolis) and Kawagoe castle (Saitama prefecture) broke the alliance of both Uesugi clans at the night battle of Kawagoe castle. Ogigayatsu Uesugi clan disappeared and Yamanouchi Uesugi clan run to Echigo province (Niigata prefecture), thus Musashi province was wholly seized by Hojo clan.

After the fall of Yamanouchi Uesugi clan, Hojo clan attacked remaining retainers including Fujita clan. Around 1550 Hojo clan suppressed Fujita clan, and Fujita clan finally subordinated to Hojo clan and adopted Ujikuni Hojo (1548-1597), the fourth son of Ujiyasu Hojo (1515-1571), the leader of Hojo clan. 

Ujikuni Hojo entered Tenjinyama castle as the leader of Fujita clan thus former leader moved to neighbor Yodo castle and changed their surname to Yodo clan. At this time also Oichi clan followed to Hojo clan and accepted Ujiteru Hojo (1542-1590), the third son of Ujiteru. Tenjinyama castle might be renovated as a main base of relative of Hojo clan.

Structure of Tenjinyama castle

Tenjinyama castle spreads over a narrow ridge which spreads north and southward.  Central area is a narrow oblong shaped area of about 20 meter long, where a ruin of castle like watchtower stands. Surrounding central area there are several terraces built at the slope.

At the south of central area, there is a large terrace of secondary area which is about 150 meter long. It might be originally separated by dry moats but became flat by the construction of the park. But structure of southern edge which has the combination of two dry moats well remains, and stone walls of eastern wall also partially remains.

At the east slope of the mountain, there is a ruin of front forts surrounded by dry moats, and line of low height stone wall. This part might be added by Hojo clan to increase the security of the castle, as western slope is protected by Ara-kawa river and eastern slope might be the target of enemy attack. Total size of the castle is over 300 meter long and one of the largest castle in Chichibu area.

Change to guard fort of Hachigata castle

In 1568, Hojo clan broke with its ally Shingen Takeda (1521-1573), the warlord of Kai province and already held western and middle part of Kozuke province. As a commander of north part of Kanto plain, Ujikuni Hojo had to manage north part of Musashi province and east part of Kozuke province, and Tenjinyama castle was too inside of the mountain.

Tenjinyama castle itself was a medium sized castle at low height hill, and might be the target of Takeda army which was good at mountain battle from Chichibu Oukan road. Ujikuni moved to Hachigata castle (Saitama prefecture) which located at flat area and easy to expand, and was also close to the center of the territory of Ujikuni.

But Tenjinyama castle kept its importance by changing its character from main base to the last fort of Hachigata castle from westward. Corridor terraces of western slope and front forts of east slope might be added reflecting this situation. At this time Takeda army actually attacked Hachigata castle but it might be a power reconnaissance then soon turned their army. 

Afterward of castle

After the death of Ujiyasu Hojo, his successor Ujimasa Hojo (1538-1590) agreed with Shingen again and the situation became stabilized again. But in 1579 Hojo clan and Katsuyori Takeda (1546-1582), the successor of Shingen Takeda, broke again. Declined Takeda clan was superior to Hojo clan at Kozuke province, but was ruined by central ruler Nobunaga Oda (1534-1582) in 1582.

Finally in 1590, Hojo clan did not subordinate to next central ruler Hideyoshi Toyotomi (1537-1598) was ruined by overwhelming army of Hideyoshi. Ujikuni Hojo firmly kept Hachigata castle against overwhelming Toyotomi army for one month but finally opened the castle. 

This time Ujikuni might gathered army from surrounding castles thus Tenjinyama castle might be not included in the battle. After the battle Hojo clan lost whole territory, and Tenjinyama castle was abolished at this time. Nobuyoshi Fujita (1559-1616), the successor of original Fujita clan, once became a feudal lord of Nishikata castle (Tochigi prefecture) under Edo Shogunate but was later lost territory the the history of the clan ended.

There remains no building and partially destructed by the construction of the park, major part of structure still remain on the mountain. Remnants at east slope is well remained and has massive impression but there is no clear road on sheer slope and careful approach is necessary. Difference of hilltop area and halfway part shows the change of the role and structure of the castle.


30 minutes walk from Chichibu Tetsudo line Higuchi station to Shiratori Shrine at hillside. 30 minutes drive from Kanetsu Jidosha-do Expressway Hanazono interchange.

Related Castles

Hachigata Castle -Four brothers led Hojo clan-
Nishikata Castle -Castle of lord who brought fortune to others but not to himself-


Pictures (click to enlarge)

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