Monday, November 5, 2018

Obora Castle -Died in the last battle-

Obora Castle

-Died in the last battle-



Name: Obora castle (Obora-jo)
Alias: Hitotsuyanagi-jo (Hitotsuyanagi castle)
Place: Tominoho Seki city, Gifu
Location: 35.593267451931624, 137.01623998187824
Type: Mountain Castle
Built: 16th century
Remaining remnants: Stone walls and clay walls 

Brief History

Obora castle (大洞城) is built on Atagoyama mountain, one of about 120 meter height at the meeting point of Mugi-gawa river and its tributary Mugikura-gawa river. Castle site stands at the middle of the valley of Mugi-gawa river which prolongs over 20 kilometer toward northeast from Seki city, and at the side of meeting point of Mugi-gawa river and Nakanoho-gawa river.

As Mugi-gawa river flows in parallel with Nagara-gawa river which comes from Gujo city and Hida-gawa river which starts Takayama area or Gero area to the center of Mino province (Gifu prefecture), Mugi-gawa river area is an important connecting point between Gujo area and Gero area. Furthermore, Mugi-gawa river and Nakanoho-gawa river was used as Hida-Nishi Kaido road, which connected Gifu area or Seki area and Takayama area in the shortest distance.

Origin of Ohora castle

Precise year is unknown but Obora castle might be built by local lord Usami clan in the former half of 16th century. In the middle part of 16th century, middle part of Mino province was managed by Nagai clan, an important retainer of Saito clan, and Mugi area which includes Obora castle also belonged to Saito clan.

But since the middle of 1560’s, Nobunaga Oda (1534-1582) who was the lord of Owari province (western half of Aichi prefecture) started invasion to the middle part of Mino province. Utilizing plots and military power Nobunaga fell several castles of this area, and finally captured this area by falling Seki castle of Nagai clan next year.

Saito clan which lost its major territory significantly lost their power, and looking at this situation important retainers at the west part of the province turned to Nobunaga. Finally Nobunaga fell Inabayama castle (later Gifu castle), the main base of Saito clan in 1567, thus Saito clan and Nagai clan ended their histories as warlords.

Expansion by Naosue Hitotsuyanagi

At this point Nobunaga allied with Shingen Takeda (1521-1573), the warlord of Kai province (Yamanashi prefecture) also held Shinano prefecture (Nagano prefecture). Shingen had a strong army lead by brave generals, and after the occupation of Suruga province (middle part of Shizuoka prefecture), next target of Shingen might be Nobunaga and his ally Ieyasu Tokugawa (1543-1616).

Around this time Shingen controlled Hida province through local lord such as Ema clan or Mitsuki clan. Besides, Endo clan which reigned Gujo area followed to Nobunaga, but it had strong relationship with Nagai clan, and it might connect to Shingen to revenge against Nobunaga.

Facing this situation, Nobunaga had to prepare against Shingen and Endo clan, and protect Seki area which was an economic center of the middle part of Mino province. Around 1570, Nobunaga ordered his retainer Naosue Hitotsuyanagi (1546-1590), who was originally a small local lord of Gifu city. Naosue significantly improved Ohora castle and named as Hitotsuyanagi castle.

Structure of Obora castle

Obora castle spreads over the peak of the mountain about 100 meter long square. Central area of the castle is a roughly square shaped one of about 20 meter long. This area had entrance with slope at its northeastern corner, and had main building at small height at the center of area where small shrine exists. 

Central area might be fully protected by stone wall and most part went broken. At the east of central area there is lower terrace equips stone walls, and stone walls of this part relatively remains, At the west of the area there are also terraces built at the slope, and there is a small stone wall at the entrance into this part from south half of the castle.

South half of the castle has a large flat area of 30 meter long and 20 meter wide, which might be the ground of hilltop residence of the lord. A valley spreads from the gap of the north half and south half toward east is also a main climbing road from hillside, and there was a main gate area protected by stone wall. Generally it is small but well protected castle.

Promotion under Hideyoshi Toyotomi

In 1573, Shingen died in ill on the way of his campaign against Nobunaga and Ieyasu. As the pressure to Mino province declined, thus Naosue was attached to Hideyoshi Hashiba (1537-1598, later Hideyoshi Toyotomi) who activated against the battle of Azai clan of Omi province (Shiga prefecture) and became the lord of Odani castle (Shiga prefecture) after the fall of Azai clan.

Naosue became Kihoro-Shu, the guard of Hideyoshi along with Tomonobu Bito (?-1590) or Masaharu Mikoda (?-1587) and activated at many battles. Hideyoshi promoted to the regional commander of Nobunaga, and after the sudden death of Nobunaga in the incident of Honnoji in 1582, Hideyoshi succeeded the position of Nobunaga and was close to next ruler.

Losing many colleagues by battle or accidents, Naosue survived many battles and promoted to the general of army. Because of his braveness and sincere character, Hideyoshi favored Naosue and used as one of the aides of his planned successor Hidetsugu Toyotomi (1568-1595). Naosue also once became the commander of Ogaki castle (Gifu prefecture), an important castle at the western part of Mino province.

Killed in the last battle

In 1590, Hideyoshi started his campaign against Hojo clan, which was the lord of Sagami province (Kanagawa prefecture) and held most part of current Kanto region. Hideyoshi already captured middle part and western part of Japan, and this becomes his last battle to unify Japan. 

But Hojo clan which expected inevitable battle strengthened their border castles including Yanamaka castle (Shizuoka prefecture), the western gate of Hakone mountains. Hideyoshi had overwhelming army ordered Hidetsugu to assault Yamanaka castle, to enhance the authority of his successor. Naosue attacked Taizaki Kuruwa, a front side fort of Yamanaka castle as a vanguard of Toyotomi army.

However, Yamanaka castle was a secure castle protected by deep moat and high clay wall, and Hojo clan brought many matchlock guns. It was a last time to render services, and his former colleagues were expelled by failure in the battle in the past. Naosue forcibly attacked Hojo army but faced strong resistance and was finally shut then died in the battle.

Afterward of Hitotsuyanagi clan

Finally Yamanaka castle fell in one day as planned by Hideyoshi, and by quick encirclement of Odawara castle as next step stopped activity of Hojo clan and contributed to the victory of Hojo clan. But Hideyoshi was deeply discouraged by hearing the death of Naosue. Four month after Hideyoshi ruined Hojo clan and unified Japan, and Naosue exactly died in his last battle, like a typical plot of novels or movies.

Other aid of Hidetsugu such as Kazutoyo Yamanouchi (1545-1605) or Kazuuji Nakamura (?-1600) became a large lord under Hideyoshi and next ruler Ieyasu Tokugawa, and if alive there was a possibility for Naosue to be a large lord. But younger brother of Naosue survived and Hitotsuyanagi clan could continue as small feudal lords.

After the move of Naosue, Ohora castle might be managed by Toshiharu Saito (1541-1582), the lord of Kajita castle (Gifu prefecture). After the incident of Honnoji, Ohora castle becomes the territory of Inaba clan which became the lord of Gujo area at Gujo Hachiman castle under Toyotomi government, instead of Endo clan. 

Aftgerward of castle

Inaba clan strengthened its main base Gujo Hachiman castle (Gifu prefecture) and branch castles including Ohora castle, preparing for the revenge of Endo clan which fell into small lord but remained at next area. At the battle of Sekigahara in 1600, Endo clan raised their army and attacked Ohora castle then Gujo Hachiman castle. After the battle Ohora castle might be abolished.

Today no building was left but structures of the castle well remain on mountain. Even though a lord of short period, the name of Naosue remained as Hitotsuyanagi shrine at the east hillside of the mountain and another name of the castle as Hitotsuyanagi castle. 

Naosue could not seize his glory at his last step, but his colleagues once became large feudal lords under Edo Shogunate were being feared and expelled by Edo Shogunate except for Kazutoyo Yamanouchi. Hitotsuyanagi family could survive as feudal lord because of its smallness, and it is an ironical result of accident totally different and unwanted from the will of Naosue himself.


30 minutes drive from Tokai Kanjo Jidoshado Expressway Tomika-Seki interchange. 20 minutes walk from entrance of climbing road at Inari Shrine (Hitotsuyanagi Shrine) but be careful for rough road covered by fallen trees.

Related Castles

Yamanaka Castle -Clay fortress guarded Hakone pass-
Gujo Hachiman Castle -White wall castle at town of clear stream-

Pictures (click to enlarge)

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