Tuesday, July 28, 2020

Sanuki Castle -History of peninsular brave (9) revival victory extend history of Satomi clan-

Sanuki Castle

-History of peninsular brave (9) revival victory extend history of Satomi clan-



Name: Sanuki castle (Sanuki-jo)
Place: Sanuki Futtsu city, Chiba
Type: Mountain Castle
Built: 15th century
Remaining remnants: Stone wall, clay walls and moats 

Brief History

Continued from Part 8

Sanuki castle (佐貫城) spreads over Shiroyama hill, one of about 50 meter height from hillside between Kitakami-gawa river and Some-kawa river, at the center of current Futtsu city. Castle site exist at the end of small valley formed by Some-kawa river, about 1 kilometer apart from coast line of Uraga-Suido straight at the mouth of Tokyo-bay.

Sanuki area is a small valley but it is an important area of communication where Boso-Oukan, a main route of west coast of Boso peninsula from Funabashi area to Tateyama area, and east and westward road from Kururi area meets. Furthermore, at Hachiman area of coast line, coastal trade toward Uraga area was performed.

Origin of Sanuki castle

Precise year is unknown but Sanuki castle might be built by Mariyatsu Takeda clan which was the lord of Mariyatsu castle (Chiba prefecture) and once extended their territory toward major part of Kazusa province (middle part of Boso peninsula) around 1500. 

Mariyatsu Takeda clan built Sanuki castle at north, Minegami castle on upstream of Minato-gawa river at southeast, and Tsukuroumi castle on the coast at southwest. These triangle placed three castles secured east coast of Uraga-Suido straight, to secure the control of straight and access to Miura Peninsula opposite of straight by sea.

Under Jokan Mariyatsu (?-1534), Mariyatsu Takeda clan experienced its peak period. Supporting Yoshiaki Ashikaga (?-1538), the younger brother of Takamoto Ashikaga (1485-1535) who was Koga Kubo Highness, as Oyumi Kubo Highness, Mariyatsu clan tried to establish their hegemony over Kanto region.

Capture by Satomi clan

However, Mariyatsu clan became inferior to Hojo clan which was the warlord of Sagami province (Kanagawa prefecture) then captured Edo castle (Tokyo metropolis) and coastal area of Tokyo Bay, and became divided for the response to internal conflict of Satomi clan. 

Jokan Mariyatsu was forced to die by Yoshiaki Ashikaga who tried to surpass Mariyatsu Takeda clan and became independent lord, then Mariyatsu Takeda clan was mobilized to the first battle of Konodai against Hojo army in 1538 by Yoshiaki Ashikaga. But at that battle Yoshiaki Ashikaga was fatally defeated and died in the battle, and Mariyatsu Takeda army also suffered severe damage.

After the battle, the territory of Mariyatsu Takeda clan became a good target for Hojo clan which won the battle, and also for Satomi clan which was Oyumi Kubo side but left battlefield in advance and conserved its army. Satomi clan seized major part of Kazusa province, and set up a horizontal defense line between Sanuki castle at west coast, Kururi castle at center and Katsuura castle at east coast.

In 1550’s, Hojo clan once settled the battle against Yamanouchi Uesugi clan at northward, and entered into the triangle treaty with Takeda clan and Imagawa clan, turned their army to Boso peninsula. Before overwhelming Hojo army, Yoshitaka Satomi (1507-1574) once seized most part of Kazusa province had to retreat their army.

Struggle between Satomi clan and Hojo clan

As Satomi navy resided at west coast of Boso peninsula was a severe treat to Hojo clan which had Miura peninsula as territory opposite of Uraga-Suido straight, Sanuki castle became the target of struggle for Hojo clan and Satomi clan. From 1555 to 1563 Hojo clan captured Sanuki castle two times but Satomi clan recovered both time.

During this struggle, in 1562, Yoshiuji Ashikaga (1541-1583) who was Koga Kubo but had to leave Koga castle (Ibaraki prefecture) before the attack of Kenshin Uesugi (1530-1578), the warlord of Echigo province (Niigata prefecture), resided at Sanuki castle as a temporally base. But next year Satomi clan captured Sanuki castle from Hojo clan, then Yoshiuji Ashikaga moved to Kamakura city from Sanuki castle.

Satomi clan at this time allied with Kenshin Uesugi, and Kenshin Uesugi continuously marched to Kanto region in the former half of 1560’s. As Hojo clan had to cope with the invasion of Kenshin Uesugi, the pressure to Satomi clan became weakened, and Satomi clan could stabilized their defense line between Sanuki castle and Kururi castle. 

Yoshitaka Satomi stayed at Kururi castle as main base, and broke the attack of Hojo army to Kururi castle in 1564. Yoshitaka placed his son and successor Yoshihiro Satomi (1530-1578) at Sanuki castle, then Sanuki castle was strengthened into a huge fortress as a forefront castle toward Hojo army.

Structure of Sanuki castle

Core part of Sanuki castle spreads over large size hill at the center of castle, which consists of central area, secondary area and third area. Central area and secondary area is a large frat area of about 100 meter long square, which are separated by dry moat. Third area is a frat terraces between two ridges, later used as ground for administrative building and now used for parking space.

At the west and east of core areas, narrow ridges spreads from core part of the castle are fortified into line of pass, small terrace at diverging point and horizontal dry moat at the end like a synapse. This synapse like structure are common element of the castle of Satomi clan such as Kururi castle or Katsuyama castle, to compensate low height hill and keep distance from the enemy.

Furthermore, hills surrounding castle site outside of two rivers were also fortified as forefront forts. Core part of the castle is about 300 meter long and not so large, but including outer areas and forefront forts total size of the castle is about 1,000 meter long square. It is equivalent to Kururi castle, and suitable for major tactical base of Satomi clan in Kazusa province.

Suppress of Hojo army to Satomi clan

In 1566, Kenshin Uesugi who marched to Shirai castle (Chiba prefecture) at the root of Boso peninsula to support and connect with Satomi clan suffered severe defeat. Looking at this failure of Kenshin, major local lords of Kanto region turned to Hojo clan then Kenshin lost his foothold in Kanto region and could not march to east part of Kanto region any more.

Utilizing this situation, Hojo clan increased pressure to Satomi clan and preceded Mifune-yama hill, about 3 kilometer north of Sanuki castle. At this point Masaki clan at Katsuura castle (Chiba prefecture) left Satomi clan before pressure of Hojo clan, and Hojo navy directly attacked Tateyama area, the center of Satomi clan at Awa province (south end of Boso peninsula).

If Sanuki castle was lost, Hojo clan could attack the base of Satomi navy at west coast of peninsula such as Tsukuroumi castle or Okamoto castle, and Satomi clan could not compete with Hojo navy any more. By doing so, Hojo army could capture Awa province by amphibious operation using land army marched through Boso-Oukan road and Hojo navy came from Miura peninsula, and this might be a result in the fall of Satomi clan.

Revival victory of Satomi army at Mifune-yama

Facing this situation, Yoshihiro Satomi attacked Hojo army stayed Mifune-yama hill to obstruct fort construction. Looking at this attack, Ujimasa Hojo (1538-1590), the leader of Hojo clan himself visited Mifune-yama, along with his general Ujisuke Ota (1542-1567).

Satomi army was totally outnumbered but knowing the geography annoyed Hojo army by night attack. Then Satomi army seemed to made total attack to Hojo army but retreated, and Hojo army looked this thought Satomi army lost the will and chased Satomi army going down from the height.

But this was a trap of Satomi army and they hided Noritoki Masaki (1549-1581), the successor of Tokishige Masaki (1513-1561) and leader of Otaki Masaki clan. Satomi army lured Hojo army to muddy area and hidden troop of Masaki army attacked them, then Hojo clan fell into confusion and retreated. Ujisuke Ota served rearguard died in the battle.

Hojo clan once broke overwhelming army at the night battle of Kawagoe castle in 1546, but in the latter half of 16th century Hojo clan well organized local lords and had superior troops but lost the critical battle several times, including the battle of Mimase-Toge in 1568, battle of Kurokoma in 1582 and this battle of Mifune-yama. The result of this battle postponed the unite of Kanto region by Hojo clan 10 years later, and also extended the history of Satomi clan same period.

Agree of Satomi clan and Hojo clan

Satomi clan won the battle of Mifune-yama again marched to the north half of Kazusa province and Shimousa province, but even losing the battle the territory and power of Hojo clan increased year by year. Kenshin Uesugi and Hojo clan temporally allied in 1569 then Satomi clan could not expect the support of Kenshin Uesugi anymore.

At this time Hojo clan firmly seized Shimousa province capturing Sekiyado castle (Chiba prefecture) in 1574, and also firmly kept major local lords of Shimousa province such as Hara clan or Sakai clan. Now the probability of Satomi clan to reverse the situation was quite low, and Yoshitaka Satomi who bravely fought with Hojo clan died in ill in 1574.

Considering inferior situation, Yoshihiro Satomi who succeeded Yoshitaka Satomi had to coordinate with Hojo clan in 1577. Satomi clan gave up the north half of Kazusa province, but still kept the line of Sanuki castle, Kururi castle and Katsuura castle as their border. Just after this coordination Yoshihiro Satomi died in 1578, and Satomi clan entered into internal conflict but Hojo clan did not intervene then border line was still kept.

Afterward of castle

In 1590, Hojo clan was ruined by central ruler Hideyoshi Toyotomi (1537-1598). Satomi clan finally belonged to Hideyoshi, but being blamed for their military operation at Miura peninsula across Tokyo Bay ignoring the order of Hideyoshi, Kazusa province was confiscated from Satomi clan the was given to Ieyasu Tokugawa (1543-1616) who succeeded the former territory of Hojo clan.

Under Edo Shogunate established by Ieyasu Tokugawa in 1603, Sanuki castle was basically a base of small domain, having vacancy periods. Use of castle might be limited to core area, and stone wall at the entrance of third area, where the residence of the lord resided, was added.

Yoshiyasu Yanagisawa (1659-1714) who extraordinary promoted to Tairo position under fifth Shogun Tsunayoshi Tokugawa (1646-1709) and became the lord of Kofu castle (Yamanashi prefecture) or Yamato Koriyama castle (Nara prefecture) once served as the lord of Sanuki castle in youth for four years. Finally Sanuki castle was abolished at the time of Meiji Revolution.

Now no building remains but structure of the castle including dry moats built by digging rock or stone wall at entrance well remains. The area open to observation is limited and seems small, but outer area continues long without entrance. This shape of castle resembles the shape of Satomi army that hided their ability and finally broke the overwhelming Hojo army with their leader.

Continue to Part 10


30 minutes walk from JR West Fukushio-sen line Kamitode station. 30 minutes drive from Sanyo-do Expressway Fukuyama-Higashi interchange.

Related Castles

Usui Castle -History of peninsular brave (8) Joint struggle with god of war-
Okamoto Castle (Awa) -History of peninsular brave (10) retreat and restructuring-

Pictures (click to enlarge)

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