Saturday, August 8, 2020

Ozawa Castle -Castle at rear mountain of residential area with record of battles-

Ozawa Castle

-Castle at rear mountain of residential area with record of battles-



Name: Ozawa castle (Ozawa-jo)
Place: Sugesengoku Tama-ku Kawasaki city, Kanagawa
Type: Mountain Castle
Built: 13th century?
Remaining remnants: Clay walls and dry moats 

Brief History

Ozawa castle (小沢城) is located at Tenjinyama hill, one of about 60 meter height from hillside at the border of Kawasaki city and Inagi city. Castle site is a peninsular like plateau spreads from Tama-Kyuryo hill, between Misawa-gawa hill and creek. From castle site, opposite of Tama-gawa river, Fuchu area which was former center of Musashi province exists.

The line of Tama-Kyuryo hill spreads east and westward at the south of Tama-gawa river was a natural defense line for Kamakura city toward north. There are several roads crossed Tama-Kyuryo north and southward, and castle site is at the middle of Kamitsumichi (mountain side) and Nakatsumichi (middle part) of Kamakura Kaido road. Near castle site side roads such as Koremasa-michi or Takauji Ashikara road exist.

Origin of Ozawa castle

Precise year is unknown but it is said that Ozawa castle was built by Shigenari Inagi (?-1205), a retainer of Kamakura Shogunate. Shigenari Inage was originally a people of Chichibu clan, a local lord of Chichibu area but followed to Yoritomo Minamoto (1147-1199), the founder of Kamakura Shogunate and became its retainer.

Shigenari Inari married with younger sister of Masako Hojo (1157-1225), the wife of Yoritomo Minamoto. Shigenari achieved Inage manor, which spread at west river side of Tama-gawa river in the north part of current Kawasaki city. Yoritomo trusted Shigenari and gave him a mission to protect the northward of Kamakura city at the line of Tama-Kyuryo height and Tama-gawa river.

Shigenari Inari activated at the battles of Minamoto army at battles such as the battle of Ujigawa, battle of Ichinotani or battle against Oshu Fujiwara clan. After the loss of his wife Shigenari became a monk and left Ozawa castle to his son, then built Masugata castle at the downstream of Tama-gawa river and moved. But finally Shigenari was involved in the internal conflict of Shogunate and was killed in 1205.

Battle at fall of Kamakura Shogunate

At the final moment of Kamakura Shogunate in 14th century, Yoshisada Nitta (1301-1338), a lord of Nitta manor at Kozuke province (Gunma prefecture), raised his army against Shogunate and gathered anti Shogunate lords. Facing overwhelming army of Yoshisada, Kamakura Shogunate tried to intercept it utilizing line of hills and rivers.

In 1333, once broken by Kamakura Shogunate army, Yoshisada finally won the battle of Bubaigawara over Shogunate army, about 5 kilometer northwest of Ozawa castle. Next Yoshisada Nitta crossed Tama-gawa river and broke Shogunate army at the battle of Sekido, about 6 kilometer west of Ozawa castle, 

As Shogunate army used Tama-gawa river and Tama-Kyuryo as a defense line, Ozawa castle might be used Shogunate army this time. But due to two time defeat Shogunate army collapsed, then Yoshisada Nitta rushed into Kamakura city, the main base of Kamakura Shogunate, and finally ruined Shogunate.

After the fall of Kamakura Shogunate, Takauji Ashikaga (1305-1358), another large local lord of Ashikaga manor at Shimotsuke province (Tochigi prefecture) and also contributed to the fall of Kamakura Shogunate, established his own Muromachi Shogunate after the conflict with Emperor Godaigo (1288-1339) who lead the South Court.

Battle inside Ashikaga clan

But inside Muromachi Shogunate, Takauji and his sons became confront with Tadayoshi Ashikaga (1306-1352), the younger brother of Takauji and lead the administration of Shogunate. In 1351, Tadayoshi seized Kamakura city and raised his army, against Takauji and his sons who kept Kyoto city.

Takauji sent large army to Kamakura city, and broke the army of Tadayoshi at Satta Toge pass of Suruga province (middle part of Shizuoka prefecture) and Odawara area of Sagami province (Kanagawa prefecture). Furthermore, this time the supporter of Takauji attacked Kamakura city from northward, across Tama-gawa river and Tama-Kyuryo hills.

In 1351, Tsunezumi Koma (?-?), the retainer of Takauji Ashikaga, attacked Ozawa castle protected by the army of Tadayoshi Ashikaga. Ozawa castle fell at this time and burnt town, then in the beginning of next year Tadayoshi was captured by the army of Takauji Ashikaga and soon died.

Disorder of Kanto region

After the defeat of Tadayoshi Ashikaga, Kanto region was governed by Kamakura Kubo Highness, the descendant of Takauji Ashikaga and a representative of Shogunate in Kanto region. But Kamakura Kubo Highness who tried to be an independent power became confront with Kanto Kanrei, the chancellor appointed by Shogunate, and Shogunate itself.

After the long battle in the latter half of 15th century Koga Kubo Highness renamed from Kamakura Kubo Highness and Uesugi clan of Kanto Kanrei divided Kanto region into west half and east half.

Furthermore, in the west half of Kanto region seized by Kanto Kanrei, the conflict between its main family Yamanouchi Uesugi clan and branch family Ogigayatsu Uesugi clan occurred. Yamanouchi Uesugi clan held north part, and Ogigayatsu Uesugi clan had south half, but Hachioji area which was held by Oishi clan and under the control of Yamanouchi Uesugi clan. 

After the purge of its excellent general Dokan Ota (1432-1486), Ogigayatsu Uesugi clan fell into inferior situation against Yamanouchi Uesugi clan. As Yamanouchi Uesugi clan had Hachioji area, the upstream of Tama-gawa river, there was a fear that Yamanouchi Uesugi clan proceeds southeastward along with Tama-gawa river to separate the territory of Ogigayatsu Uesugi clan. Preparing for this Ozawa castle might be expanded by Ogigayatsu Uesugi clan.

Structure of Ozawa castle

Ozawa castle spreads over the line of ridge having three small peaks. The east peak named Senganyama is used main area of the castle, which might equip watching tower. At the south slope of this peak, large flat area of about 40 meter long and 10 meter wide built by flattening the ridge, which might be used as commanding place of the general.

At the southwest of central area, utilizing small valley there is a large flat are of about 50 meter long and 20 meter wide, which might be used for the ground of the hillside residence. Entrance to hilltop area from hillside flat space is separated by the gate surrounded by clan wall. At the east of central area narrow path prolongs about 100 meter, to the edge of the hill with small flat spaces.

At the west of central area, there is a main entrance of the castle utilizing the peak of Tenjinyama. Westward of this area is separated by the line of huge dry moat, end entrance route passes roundly around the side of this peak, to enable attack from hilltop to entering enemies. Further at the west of entrance area there is large flat area with no clear remnant, and it might be used as a camping space.

Battle of two Uesugi clans

In 1504, Tomoyoshi Uesugi (1473-1518), the leader of Ogigayatsu Uesugi clan, asked reinforcement from Soun Hojo (1456-1519) and broke the army of Yamanouchi Uesugi clan at the battle of Tategawara. At this battle Hojo army stayed at Masugata castle, and might pass Ozawa castle then crossed Tama-gawa river and entered the battlefield.

At this battle Ogigayatsu Uesugi clan broke Yamanouchi Uesugi clan, but Yamanouchi Uesugi clan summoned reinforcement army from their territory Echigo province (Niigata prefecture) and shut the backward of Ogigayatsu Uesugi territory. Tomoyoshi Uesugi encircled at Kawagoe castle (Saitama prefecture) surrendered to Yamanouchi Uesugi clan.

However, utilizing the conflict between two Uesugi clan, Hojo clan gradually expanded their territory from Odawara castle (Kanagawa prefecture), at the west edge of Kanto plain. Hojo clan ruined Miura clan which spread at Miura peninsula in 1518, then next proceeded to east part of Sagami province.

Battle of Hojo clan and Uesugi clan and afterward

Ujitsuna Hojo (1487-1541), the successor of Soun Hojo, captured Edo castle (Tokyo metropolis) which was the core castle at the south edge of Musashi province (Tokyo metropolis) in 1524. Hojo army tried to keep Edo castle and Ogigayatsu Uesugi army aimed to recover it fiercely fought around Tama-gawa castle in 1530’s.

In 1530, Hojo army lead by Ujiyasu Hojo (1515-1571), the successor of Ujitsuna Hojo, fought with the army of Ogigayatsu Uesugi clan stayed at Jindaiji castle (Tokyo metropolis) at the opposite of Tama-gawa river. Ujiyasu Hojo was still 16 years old and this was his first battle but Ujiyasu broke Ogigayatsu Uesugi army.

In 1537, Hojo army detoured Jindaiji castle and directly attacked Kawagoe castle, the last main base of Ogigayatsu Uesugi clan then fell it. As the front line moved northward from Tama-gawa river, Further Ogigayatsu Uesugi clan itself was ruined at night battle of Kawagoe in 1546, then both of Ozawa castle and Jindaiji castle might be abolished at this time.

Now no building remains but structure of the castle well remain on the mountain, even though development approached just the next to the castle. Too narrow ridge of the mountain which limited the possibility of the castle ironically saved the castle from development. It is valuable that the castle with the record of actual battle is preserved just at the next of houses and parks, with accessibility of just 10 minutes walk from station. 


10 minutes walk from Keio Sagamihara-sen Keio Yomiuri-Land Mae station. 20 minutes drive from Chuo-do Expressway Inagi interchange to parking of Yomiuri Land. Entrance is at the middle of climbing road to Giants Stadium.

Related Castles

Jindaiji Castle -Same plan and structural progress (1)-


Pictures (click to enlarge)

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