Thursday, October 24, 2019

Nukuyu Castle -Too much for small local lord (1)-

Nukuyu Castle

-Too much for small local lord (1)-



Name: Nukuyu castle (Nukuyu-jo)
Place: Kawamoto Kawamoto town, Shimane
Location: 34.98087963617778, 132.50132193368802
Type: Mountain Castle
Built: 14th century
Remaining remnants: Clay walls and dry moats 

Brief History

Nukuyu castle (温湯城) is located at a mountain of about 150 meter height from hillside, between Aishita-gawa river and Yatani-gawa river both are tributaries of Gonokawa river. Castle site is at the backside of Kawamoto town, which is the center of inland area in the east part of former Iwami province (west half of Shimane prefecture).

Gonokawa river which flows northward from Chugoku mountains faces Hakusan volcano line which spreads along the coast of the Sea of Japan in Chugoku region, and turns westward and runs 30 kilometer horizontally, then turns northward again and flow into the sea. Kawamoto area is at the center of this horizontal flow of Gonokawa river.

Formerly river transportation prospered at Gonokawa river between Miyoshi city and Gotsu city, but because of deep valley and its winding shape it was not suitable to walk along the river. Then mountain road directly connects upstream and coast was used, and Kawamoto area was the junction of river transportation and inland road.

Furthermore, at 15 kilometer north from Kawamoto area, Iwami silver mine which was formerly the largest one in Japan exists. Because of its value and weight silver ingot was transported by land transportation, and Kawamoto area was a transfer station toward south. Furthermore, as Gonokawa river runs southward and westward of silver mine area like natural water moat, control of Gonokawa river was also fatal for control of silver mine.

Origin of Iwami Ogasawara clan

Precise year is unknown but Nukuyu castle was built by local lord Iwami Ogasawara clan. Ogasawara clan which was known as the governor of Shinano province (Nagano prefecture) then turned into feudal lord was originally a branch family of Minamoto clan lived at Kai province (Yamanashi prefecture).

At the establishment of Kamakura Shogunate in 1192, Ogasawara clan became the governor of Shinano province due to their achievement. Furthermore, Ogasawara clan activated at the battle of Jokyu in 1221, and further achieved Awa province (Tokushima prefecture). Miyoshi clan which built their hegemony at Kinki region around 1550 was a descendant of this Ogasawara clan.

One of this Ogasawara clan at Awa province made achievement at the invasion of Chinese Yuan Dynasty. As Ogasawara clan protected the coast of Iwami province for the assault of the enemy, after the campaign Ogasawara clan achieved Oochi providence including Kawamoto area.

Build of Nukuyu castle

At this point Iwami silver mine was not found thus its territory was a quiet mountainous valley. At first Iwami Ogasawara clan lived at current Misato town, about 10 kilometers apart from Kawamoto area. But in 1333, after the fall of Kamakura Shogunate, Iwami province was involved into the conflict between Emperor Godaigo (1288-1339) and Muromachi Shogunate.

Facing this situation, Iwami Ogasawara clan belonged to Shogunate and broke Emperor side army at the battle of Mikusu near Iwami silver mine. As a reward for this achievement, Mihara area at the north of Gonokawa river was given. Iwami Ogasawara clan newly built Nukuyu castle at the place of Kawamoto, at the middle of their old territory and new territory.

During the internal conflict between Emperor and Shogunate, Ouchi clan which was the governor of Suo province (east half of Yamaguchi prefecture) managed Iwami province through large local lords in the west part of the province such as Yoshimi clan at Tsuwano castle (Shimane prefecture) or Masuda clan at Nanao castle (Shimane prefecture).

During Muromachi era, Iwami Ogasawara clan gradually grew their power through the conflict with surrounding local lords, and became at the major local lord of east part of province. Especially conflict with Sawa clan which was at the east of Iwami Ogasawara clan continued over 100 years, and Ogasawara clan gradually deprived the territory of Sawa clan. Nukuyu castle was expanded along with the development of the clan. 

Structure of Nukuyu castle

Nukuyu castle is built over corned shape mountain. Main structure of the castle spreads over hilltop area and a ridge prolongs northwestward to hillside, which is the most easy approach route of the castle. Each area is built by the edge of narrow flat space, and height difference of each area is large because of the shape of the mountain.

It is quite difficult to grasp the shape of the castle, because of the collapse of terrain due to sheer slope and soft terrain, and no signboard at the ruin. Certain part of climbing road has disappeared and it is necessary to climb the slope directly. In spite of its popularity, information is quite limited because of small number of visitors due to geographical location and low accessibility.

According to the report of Shimane prefecture, central area is a two layer terrace of 40 meter long. At the east of central area there is a secondary area of same size, and east edge of this area connected to backside mountain is separated by huge dry moat. At the west of central area, there are several large terraces called as “Basenba” (horse washing place”, “Terayashiki” (residence) or ”Kurayashiki” (storage).

From hillside to halfway it is recorded that combination of dry moats are built on the slope but they are not identified. Total length of the castle is about 400 meter long, and it is worthy as a main base of major local lord. Castle town might spread over the 500 meter long valley between the castle and Gonokawa river.

Development of Iwami silver mine

In the beginning of 16th century, Ouchi clan became its peak period under Yoshioki Ouchi (1477-1529), the marched to Kyoto city and participated in the government of Hosokawa clan, But utilizing the absence of Ouchi clan, Amago clan significantly increased its power under Tsunehisa Amago (1458-1541) at Izumo province (east part of Shimane prefecture).

At the same time, Ouchi clan brought the mining technology of continent to Iwami silver mine which was operated in a small way and changed it to the largest silver mine of Japan. East part of Iwami province suddenly changed to the front of two power Ouchi clan and Amago clan, not only for the territory but also for the Iwami silver mine.

If Iwami Ogasawara clan had sufficient power they might grow as an independent power from the income of silver mine. But because of the limited territory and army, the mine was too much burden for the clan and just brought the cause of conflict. In 1528, Amago clan once intruded into Iwami province and captured the mine, but soon Iwami Ogasawara clan recovered the mine under the order of Ouchi clan.

Involvement in struggle for silver mine

However in 1540, Iwami Ogasawara clan turned to Amago clan looking at the attack of Amago clan to Mouri clan, which was the lord of Yoshida Koriyama castle of Aki province (Hiroshima prefecture) and still belonged to Ouchi clan. After that the holding of silver mine changed between Ouchi clan and Ogasawara clan under Amago clan.

In 1550, Ouchi clan virtually ruined by the rebel of its general Harukata Sue (1521-1555), and Motonari Mouri (1497-1571) who broke Harukata Sue at the battle of Itsukushima started to grow toward the ruler of Chugoku region. Motonari looked at the economic right of silver mine and once captured it in 1556.

In response to this, Amago clan sent large army with its leader Haruhisa Amago (1514-1561) and its brave general Tsunemitsu Honjo (1513-1562) to assist Iwami Ogasawara clan which was attacked by Mouri army at Nukuyu castle. But the arrival of Amago army became late because of flood of Gonokawa river, and Iwami Ogasawara clan could not stand the attack of Mouri army opened the castle and surrendered.

Fall of Nukuyu castle

However, Amago army turned to the silver mine and attacked Yamabuki castle (Shimane prefecture) at the center of silver mine. Amago army broke the reinforcement army of Mouri clan at the battle Oshihara, and captured Yamabuki castle and the mine. As Mouri army once retreated, Ogasawara clan returned to Amago clan and managed silver mine with Tsunemitsu Honjo placed at Yamabuki castle.

But in 1558, Motonari Mouri himself led large army to capture the mine. Motonari encircled Nukuyu castle on the way from Aki province to the mine, and built temporary castle at the peak of backside mountain of Nukuyu castle. Iwami Ogasawara clan asked reinforcement army to Amago clan, then Haruhisa Amago sent his army again.

However, this time Amago clan could not cross Gonokawa river due to flood again. This time Motonari tightly enclosed the castle over two month, and Nagakatsu Ogasawara (1520-1571), the leader of the clan, surrendered to Mouri clan. This time Mouri clan confiscated the territory of Nagakatsu and Nukuyu castle.

Afterward of castle

Next Mouri army attacked Yamabuki castle protected by Tsunemitsu Honjo. But Tsunemitsu firmly guarded Yamabuki castle with less soldiers, and preparing for the enemy at backside finally Mouri clan gave up the siege of Yamabuki castle. Amago army chased retreating Mouri army and broke it at the battle of Gourozaka, and could keep the silver mine and Yamabuki castle.

After the battle Nagakatsu Ogasawara held remaining small territory at the north of Gonokawa river. Amago clan kept four years, but after the death of Haruhisa Amago in 1561 the power of Amago clan significantly declined then Tsunemitsu Honjo turned to Mouri clan with the mine in 1562. Nukuyu castle might be kept under Kikkawa clan, the branch family of Mouri clan and commander of Sanin region by around 1590.

Now all building was lost but structure of the castle roughly remains in spite of the collapse. Areas of the castle maximally used narrow space of the mountain looks like the shape of Iwami Ogasawara clan struggled to survive under limited territory and power. Now Nukuyu castle silently remains at quiet village, same as the period before noisy era with the mine. 


60 minutes drive from Chugoku Jidoshado Expressway Chiyoda interchange via Route 261. Be careful for sheer slope and disappeared climbing road.

Related Castles

Yamabuki Castle -Name plate of world-leading silver mine-


Pictures (click to enlarge)