Sunday, January 13, 2019

Nanao Castle (Iwami) -Preparation for both of war and peace-

Nanao Castle (Iwami)

-Preparation for both of war and peace-



Name: Nanao castle (Nanao-jo)
Place: Nanao-cho Masuda city, Shimane
Location: 34.672595749497695, 131.86321930148816
Type: Hill Castle
Built: 13th century?
Remaining remnants: Gate (moved), clay walls and dry moats

Brief History

Nanao castle (七尾城) of Iwami province spreads over Shiroyama hill, one of 70 meter from hillside at the most inside of Hamada plain. Hamada plain is formed at the mouth of Takatsugawa-river and Masudagawa river, and one of four coastal flat area of Iwami province (western part of Shimane prefecture) along with Ota area, Gotsu area and Hamada area.

Even at the western end of province, Masuda area has the largest size flat area formed by two rivers which provided agricultural production. Also this area is a diverging point from main route of Sanindo comes from Matsue city toward Yamaguchi city, and Kitaura Kaido road heads to Hagi area. Along with Masuda port, Masuda area had been prospered area of the province.

Origin of Masuda clan and Nanao castle

Nanao castle might be built by 13th century by local lord Masuda clan. Masuda clan is said as a descendant of central noble Fujiwara clan which was appointed as the governor of Iwami province but did not return and turned into local lord. At first lived at Hamada city where providential office existed and named as Mikimoto clan.

At the establishment of Kamakura Shogunate, Mikimoto clan supported Yoritomo Minamoto (1147-1199), the founder of Shogunate from early period and activated in the battles. After the fall of Taira clan and start of Kamakura Shogunate, Mikimoto clan seized western half of Iwami province. Soon Mikimoto clan moved to Masuda area then renamed to Masuda clan.

Miyake clan moved to Masuda area resided at the most inside of Masuda plain and built their residence named as “Miyake-Odoi”. This place is a flat place of about 1 kilometer square at the both of Masuda-gawa river, surrounded by hills including Shiroyama-hill. This place is a suitable point to manage water flow of the river, accessible by ship from the Sea of Japan, and watch Sanindo road. At this point there might be a fort at castle site as a watching point.

Rise of Ouchi clan at next province

After the fall of Kamakura Shogunate, at Suo province (eastern half of Yamaguchi prefecture) at the next of Iwami province, Ouchi clan significantly grew their power. Among the conflict between the South Court and Muromachi Shogunate, Ouchi clan at first belonged to the former and broke Koto clan which was the governor of Nagato province (western half of Yamaguchi prefecture) and seized it.

However, replying to invitation from Muromachi Shogunate and looking at decline of the South Court, later Ouchi clan turned to the Shogunate and became its major retainer. Once Yoshihiro Ouchi (1356-1400) became the regional commander of Shogunate at Kyushu region and increased their territory to six provinces but was suppressed by Shogunate then rebelled but failed.

Ouchi clan once lost its power but remained as the governor of Suo province and Nagato province, then gradually regained their power through the trade with continent. At the battle of Onin which prolonged from 1467 to 1477 at Kyoto city Ouchi clan became substantial leader of the West army, and later captured north part of Kyushu island pushing out Shoni clan. In the beginning of 16th century Ouchi army marched to Kyoto city and became the supporter of Shogun, and Ouchi clan became its peak.

Prosperity under Ouchi clan

As Ouchi clan was just at the next of their territory, Masuga clan consistently followed Ouchi clan during Muromachi period. As Ouchi clan was asked to send army from Shogunate as a major governor, Masuga clan fought with Ouchi army at many place, sometimes losing their leaders. On the other hand, domestically Masuga clan expanded their territory fighting against Yoshimi clan, the local lord of Tsuwano providence.

In the end of 15th century, Masuda clan controlled western half of Iwami province by themselves and branch families such as Sufu clan or Mikuma clan. Their main base Miyake-Odoi was a large one equivalent to the residence of governors and shows the prosperity of Masuda clan. In the latter half of the century, Sesshu (1420-1506) who was a famous ink and wash painting and garden planner visited and said to die in Masuda area.

In the beginning of 16th century, Amago clan which was the local lord of Izumo province (east half of Shimane prefecture) united the province and started aggressive expansion toward surrounding providence. Eastern border of Iwami province suddenly became the front against Amago clan, thus Masuda clan fought against Amago army along with Ouchi clan but Masuda area was apart from the front.

Crisis after coup d'etat

However, in 1542, Yoshitaka Ouchi (1507-1551) who was the leader of Ouchi clan sent large army to Gassan Toda castle (Shimane prefecture), the main base of Amago clan, but faces severe defeat. Yoshiataka lost interest in politics and military and fell into the Kyoto style culture. Harukata Sue (1521-1555), the deputy governor of Suo province and managed the army of Ouchi clan, increased dissatisfaction to his master. Masuda clan had close relationship to Sue clan through marriages.

In 1551, at last, Harukata Sue raised his army against Yoshitaka Ouchi, and Masuda clan supported Harukata. On the other hand, Yoshimi clan at Sanbonmatsu castle (current Tsuwano castle) belonged to Yoshitaka because of marital relationship, then Yoshitaka tried to escape to Yoshimi clan by ship but failed by bad weather and killed himself.

Masuda clan attacked Sanbobmatsu castle along with Sue army but failed to fall it then once made peace. However, in the meantime, Motonari Mouri (1497-1571) who was the lord of Yoshida Koriyama castle (Hiroshima prefecture) once supported Sue clan to leave from Ouchi clan, broke with Takafusa and raised their army.

In 1551, Harukata Sue attacked Motonari with large army but died in the battle of Itsukushima facing sudden attack of Mouri army. Mouri clan which became the ruler of the region started to invade into remaining Ouchi and Sue territory, and Yoshimi clan became a trusted retainer of Mouri clan because of their resistance against Sue army. Contrary to this, Masuda clan fell into the enemy of Mouri clan and became the next target.

Facing this situation, Fujikane Masuda (1529-1597), the leader of Masuda clan, seek for the peace with Mouri clan but also prepared for the battle. Fujikane significantly expanded Nanao castle as a last resort, then left Miyake-Odoi residence and moved his main base to Nanao castle. Masuda clan was exactly pushed to the corner of extinction.

Structure of Nanao castle

Nanao castle spreads over “’Y” letter shaped Shiroyama mountain which has two straight line ridges from hilltop. Central area is a long and narrow one of about 20 meter wide and 80 meter long, which has a basement of watchtower at its eastern end. At the west of central area, there is another same size area which had a ruin of clay wall and stone wall where residence of the lord might exist.

At the below of central areas, there is a meeting point of two ridges at the both side of the valley. This valley might be used as a main route of the castle, and at the meeting point there is a ruin of the well. Northern ridge is higher but narrow then there are several small terraces not so shaped.

On the other hand, southern ridge is lower and expected as attack route, thus this area is securely protected by combination of sheer clay wall and narrow path run at the side of each terrace which enable attack from upper area. A small compartment at the middle of the ridge might be the main gate of the castle. Total size of the castle is about 800 meter long and 200 meter wide, and becoming to the main base of large local lord.

Resistance and subordination to Mouri clan

In 1556, Motoharu Kikkawa (1530-1586), the third son of Motonari who was known for his braveness, started to invade into Iwami province. Motoharu and Yoshimi clan attacked Masuda clan, but Masuda clan resisted over half year. Finally next year Masuda clan lost the part of their territory but was forgiven and became the retainer of Mouri clan.

At this point Mouri clan was at the final stage to ruin Sue army which stubbornly resisted, and further have to prepare against surrounding large lords such as Amago clan or Otomo clan which was the warlord of Bungo province (Oita prefecture) which are seeking the absence of Mouri army. 

Huge expansion of Nanao castle reminded Mouri army the disadvantage of long term campaign, and to confront Amago army which deprived Iwami silver mine from Ouchi army it was better to use Masuda army as a whole rather than ruining them. Masuda clan achieved survival by appropriate preparation for the battle and surrounding situation.   

Afterward of Masuda clan and Nanao castle

After the campaign, Masuda clan became a major retainer of Motoharu Kikkawa who managed Sanin region. In 1560’s Mouri clan started to siege their fatal rival Amago clan, and finally let them surrender in 1566. Masuda army activated at this battle, and further participated in battles under Motoharu Kikkawa throughout Sanin region and other place.

Motonaga Masuda (1558-1640), son of Fujikane Masuda, was excellent both at politics and military. Motonaga activated at many battles under Mouri clan which followed to central ruler Hideyoshi Toyotomi (1534-1597), such as Odawara campaign. But as a result of the battle of Sekigahara occurred in 1600, Mouri clan lost major part of their territory including Iwami castle.

At this time next ruler Ieyasu Tokugawa (1543-1616) who evaluated the talent of Motonaga recruited by guaranteeing former territory, but Motonaga refused it and remained to Mouri clan. Motonaga had to leave Masuda area but became the commander of Susa area, which are next to Masuda area, and also activated as a leading mister and succeeded in fiscal reconstruction of Mouri clan which suffered fiscal problem from the loss of its territory. Masuda clan continued as a leading retainer of Mouri clan by the end of Edo era.

Now no building except one gate moved to neighbor temple remains, but structure of the castle well remain over the hill. Ruin of Miyake-Odoi or surrounding temples with the garden of Sesshu shows cultural prosperity of Masuda area in medieval era. Not so appealing but closely looked secure Nanao castle well shows the image of Masuda clan which quietly but steadily survived turbulent era.


20 minutes walk from JR West Sanin Honsen line Hamada station to Sumiyoshi shrine at hillside. 30 minutes drive from Hamada Jidoshado Expressway Hamada interchange.

Related Castles

Tsuwano Castle -Broken promises-

Pictures (click to enlarge)

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