Wednesday, October 7, 2020

Sentoku Castle -Castle certified by record of abolition-

Sentoku Castle

-Castle certified by record of abolition-



Name: Sentoku Castle (Sentoku-jo)
Place: Sentokucho Miyako city, Iwate
Type: Hill Castle
Built: 14th century?
Remaining remnants: Clay walls and dry moats 

Brief History

Sentoku castle (千徳城) is located over a hill of about 70 meter height to which Sanriku Jidoshado Expressway penetrates, at 2 kilometer west of current Miyako city central. Miyako city is a port town at the mouth of Hei-gawa river, at the middle of Sanriku Kaigan coast and 100 kilometer apart from Hachinohe area and Kesennuma area.

Miyako area has large inlet protected by Cape Hiisaki and not directly faced outer sea, it had been an important port of the area. In Edo era, as Morioka town, the capital of Nanbu domain, is at same latitude, Miyako port was developed as an outer port of Morioka city by Nanbu clan and prospered both for fishery and transportation.

At the end of Edo era, there arouse the naval battle between former Edo Shogunate navy and Meiji new government navy at Miyako bay. Today Miyako port prospers as the basement of transport and logistics to Morioka area, along with other ports at Sanriku-Kaigan coast such as Kamaishi port or Ofunato port.

Origin of Sentoku castle and Hei clan

Precise year is not clear but Sentoku castle might be built by local lord Hei clan in 14th century. The origin of Hei clan is also not clear but is told as the descendant of Tametomo Minamoto (1139-1170), who was known for strong arrow and was the uncle of Yoritomo Minamoto (1147-1199) who established Kamakura Shogunate.

Hei clan was originally named as Sasaki clan and served to Yoritomo Minamoto. After the fall of Oshu Fujiwara clan which held whole part of current Iwate prefecture in 12th century, Kamakura Shogunate placed their retainers to the province. At this time Sasaki clan was appointed as the magistrate of Hei river area, then moved and named as Hei clan.

Hei clan originally lived at Takusari castle at the opposite of Hei-gawa river. Takusari castle was at the meeting point of Hei-gawa river and its tributary Nagasawa-gawa river, and an appropriate place to manage valleys of two rivers. Sentoku castle might be originally built as a branch castle of Takusari castle to protect eastward of the valley.

Hei clan prospered as a major local lord of the area during Kamakura era, but after the fall of Kamakura Shogunate it was involved in the conflict between Muromachi Shogunate and the South Court. Hei clan at first belonged to the South Court then turned to Muromachi Shogunate, but was attacked by Nanbu clan which earlier turned to Muromachi Shogunate in the middle of 14th century.

Arrival of Sentoku clan

Hei clan lost before Nanbu clan at this battle and was ruined, thus remaining Hei clan fell into small lords of each village subordinated to Nanbu clan. Main family of Hei clan barely remained as the small lord of Takusari castle and renamed to Takusari clan, and Nanbu clan placed their relative Ichinohe clan at Sentoku castle at the north side of Hei-gawa river, which was closer to the territory of Nanbu clan.

Ichinohe clan was originally an eldest son of Nanbu clan, but as it was born from concubine it became a branch family of Nanbu clan and resided at Ichinohe area. As Ichinohe area was at the south edge of Nanbu territory, branch families of Ichinohe clan widely spread around north half of current Iwate prefecture and northeast part of current Akita prefecture.

The detail of Sentoku clan is not clear but it is recorded that Sentoku clan resided at Sentoku castle and held Miyako area in the former half of 16th century. Sentoku castle might be expanded into a main base of Sentoku clan, to gather retainers including Takusari clan and manage Miyako area. Castle town and river port might be placed at the east of the castle between Chikauchi-gawa river and Hei-gawa river.

Structure of Sentoku castle

Sentoku castle spreads over Y letter shaped hill spreads from northwestward to southeastward. Central area of the castle is a trapezoid shaped one of about 50 meter long and 30 meter wide, which is encircled by sheer cliff of 5 meter height. Surrounding central area there is a corridor area wholly encircles the central area.

At the south of central area which is also 50 meter long and 30 meter wide, that has a layer of corridor area toward south. At the southeast of secondary area, there is a small peak now used as a ground of Hachiman-Jinja shrine that also has a layer of terraces. At the east of central area, there are lines of terraces spreads along with small ridges.

At the north of central area, ahead of dry moat, there are third area and fourth area which protect the core area of the castle from backward hills. At another line of ridge spread toward south at the opposite of Sentoku valley, there were terraces of old era named as “Furutate” or “Horiaitate” which are simple flat areas.

Probably at the time of Hei clan Sentoku castle might be limited to Furutate area or Horiaitate area which can manage the narrow flat area spreads at the westward of the hill. Later Sentoku clan expanded Sentoku castle to east ridge with large construction, to manage whole part of Miyako area and surrounding area. Total size of Sentoku castle is about 200 meter long square and largest one at Miyako area.

End of Sentoku castle

In 1580’s, Sentoku clan captured Haraikawa-date castle at Tsugaruishi area just at the south of Miyako area, and expanded their territory. Two years later in 1585, Masauji Sentoku (?-1587), the leader of Sentoku clan, was ordered from Nanbu clan to move to Asaseishi castle at Kuroishi area of Aomori prefecture.

As Masauji Sentoku allied with Tamenobu Tsugaru (1550-1608) who left Nanbu clan and became independent warlord at Tsugaru region, Nanbu army attacked Asaseishi castle but Masauji Sentoku drove back the attack of Nanbu army. But later Masauji Santoku broke with Tamenobu Tsugaru and was assassinated by Tamenobu.

At the revolt of Masazane Kunohe (1536-1591) against Nanbu clan, Sentoku clan remained at Sentoku castle kept neutral. After the end of the revolt Sentoku clan became the retainer of Nanbu clan, but in 1592 during the absence of Sentoku clan participating in foreign expedition Nanbu clan destructed Sentoku castle along with Takusari castle.

Castle abolition of Nanbu territory

According to the record of castle destructions of Nanbu clan in 1592, among 48 castles of Nanbu territory 36 castles including Sentoku castle were broken and 12 castles remained. In 1590 central ruler Hideyoshi Toyotomi (1537-1598) approved the territory of Nanbu clan and ordered to destruct all castles held by retainers and move the family of retainers to Sannohe castle (Aomori prefecture), the main base of Nanbu clan.

Hideyoshi ordered Nanbu clan to destruct all castles other than main base, but considering unsettled situation after the revolt of Masazane Kunohe and raise of local people at Hienuki and Waga area, Nanbu clan had to keep military base at border and unsettled area then 12 castles were kept as a result of compromise.

After that the decrease of castle has continued and finally only Morioka castle (Iwate prefecture) and Hanamaki castle (Iwate prefecture) were formally kept, but Sannohe castle was still maintained as a historic site and other castles substantially continued as forts or garrisons.

Reason to abolish castles

Castles were built and abolished by various reasons, and castle abolition might be classified into voluntary one and compulsory one. Of course holding castle needs defense forces and maintenance cost, tactical purpose castles were easily abolished when military threat of the area disappeared.

Border castles might be voluntary abolished as a certificate of alliance or agreement, as seen at the battle of Kawanakajima between Takeda clan and Uesugi clan. When a warlord was ruined, the main base of that warlord was sometimes destructed as it was too large for a military base of new warlord, or it was necessary to erase the authority of former warlord and change the atmosphere.

Contrary to voluntary abolition, compulsory abolition related to the control of status. Castle was a symbol of autonomy, and target of every lord and retainer from large one to small one, as described in the proverb “becoming a master of province and castle”. From reverse view, castles were obstruction of authority of warlord.

Attempt to decrease castles and autonomy

In medieval era, the warlord consists of multi-layered dominance of the lord, important retainers, middle class retainers and small samurais. Each layer held respective castles and autonomy, and large size retainers were especially held wide autonomy except for military and foreign affairs, same as the relationship of nation and state.

Some warlords tried to decrease the autonomy of retainers and tried to summon retainers around main castle and destruct castles of retainers, but this policy was opposed by retainers and castles were necessary preparing for other warlords. As a result, castle abolition proceeded under overwhelming powers of rulers both for external enemies and internal retainers.

Central ruler Nobunaga Oda at first abolished castles of Yamato province (Nara prefecture) when the revolt of Hisahide Matsunaga (1508-1577) was settled. Even though a ruler the abolition of castles would cause antipathy of retainers it was applied to newly occupied territory, to prevent the raise of former powers and place the retainers to new territories.

Castle destruction under Toyotomi government

Hideyoshi Toyotomi who became the ruler after the death of Nobunaga Oda also published the order to destruct small castles after the cease of Shikoku campaign and Kyushu campaign, Hideyoshi also ordered to Mouri clan which subordinated to Toyotomi government to clean up castles in their territory. 

But at this point mainly castles of small retainers were broken, and 10 or more branch castles still remained in each province. Each feudal lord under Toyotomi government tried to follow the order to show the loyalty and establish their own authority among retainers utilizing the order, but antipathy of retainers and necessity of security still remained.

Toyotomi government and Edo Shogunate established after the battle of Sekigahara in 1600 transferred feudal lords from their original territory to new territory, to strengthen the control to lords. At the movement retainers of the lords were separated from their original territories and small castles of retainers were mostly disappeared. 

One domain one castle rule by Edo Shogunate

But on the other hand, feudal lords transferred after the battle of Sekigahara built or reformed branch castles to manage their new territory before non obedient retainers of ruined warlords. In spite of decrease of the number, remaining branch castle were significantly strengthened equal to the main base at this period.

In 1615, Edo Shogunate which ruined Toyotomi government at the battle of Osaka castle published “Ikkoku Ichijo Rei”, one domain one castle rule. Under this rule only approved feudal domain could have one castle as main base, and branch castle or castle of small lords should be abolished. 

Due to the arrival of peace period and publish of this rule, remaining castles were mostly abolished except for the main base of each domain. But lords at marginal area such as Shimazu clan at Satsuma domain (Kagoshima prefecture) or Date clan of Sendai domain (Miyagi province) substantially kept branch castles by the name of forts.

Castle certified by record of abolition

In 1637, rebellion of residents of Shimabara peninsula (Nagasaki prefecture) occurred utilizing the remnant of Hara castle (Nagasaki prefecture) which was nominally abolished but major structure of the castle including several buildings still stood. After the cease of the rebellion, to prevent the reuse remnant of the castle were physically broken especially in western Japan. 

After the destruction of this time, the number of the castle did not change so much during Edo period. After the fall of Edo Shogunate, castles were broken to show the arrival of new period except for the ones used by new government army, and many castles disappeared by development and war damage.

Today no building remains but structure of the castle still roughly kept in the bush. The size and solid structure of remaining remnants shows Sentoku castle was an important regional base, but due to limited information the detail of the castle is quite unclear. Ironically only the record of abolition of the castle certified the existence of the castle at the port town. 


20 minutes drive from Sanriku Jidoshado Expressway Miyako-Chuo interchange. Castle area is Sentoku Hachimangu Shrine and backward.

Related Castles

Pictures (click to enlarge)

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