Wednesday, June 18, 2014

Koga Castle -Castle disappeared into embankment-

Koga Castle

-Castle disappeared into embankment-



Name: Koga Castle (Koga-jyo)
Place: Chuocho Koga city, Ibaraki
Type: Plain Castle
Built: Originally mid 16th century, expanded in 1580's
Remaining remnants: Clay walls and moats

Brief History

Koga castle (古河城) is located at the riverside of Watarase river, in the center of Koga city. Same as Sekiyado castle near this castle, Koga area was a meeting point of rivers came from different places, and an important point for river transportation. Especially Watarase river stem from north edge of Kanto region and passes large castles, Koga castle was an connecting point of south half and north half of Kanto plain. As the castle located beside large river, the situation of Koga castle was quite same as Sekiyado castle.

Build of Koga castle and Koga Kubo

Originally there was a small lodge of local lord from medieval era, but a genuine castle was built around 1450 by Shieuji Ashikaga (1438-1497), a leader of Koga Kubo clan (Koga Highness) as his residence. During Muromachi era, Kanto region was originally governed by Kanto Kubo (Kanto Highness), a house stem from younger brother of Muromachi shogun and representative of Shogunate located at Kamakura city, and Kanto Kanrei, vassal of Kanto Kubo. In 1439, Mochiuji Ashikaga (1398-1439), leader of Kanto Kubo at that time, attempted rebellion to Muromachi Shogunate but was suppressed and died in 1439. Later his son was Shigeuji was approved to restore Kamakura Kubo again in 1449. But later he lost Kamakura city and moved to Koga area where was important place of communication and close to supporting lords in 1456. His house was called as Koga kubo, and still kept the highest authority in Kanto region.

From the beginning of 16th century, Hojyo clan, a warlord of Sagami country (Kanagawa prefecture) expanded their territory beating old power of Kanto region. As a new comer, to achieve the authority to dominate Kanto region, Hojyo clan approached to Koga Highness and tried to invite them into Hojyo side. On the other hand, Kenshin Uesugi (1530-1578), a warlord of Echigo country (Niigata prefecture) and rival of Hojyo clan accepted Norimasa Uesugi (1523-1579), who had Kanto Kanrei position but was defeated against Hojyo clan and ran into Echigo country.

Kenshin succeeded the position of Kanto Kanrei and attacked Kanto region utilizing this as justification, thus Hojyo clan had to connect with upper authority. Hojyo clan was nominally a retainer of Koga Kubo, and married with Koga Kubo people. They also improved Koga castle as a residence of Koga castle, to protect the source of their authority. But main stream of Koga Kubo clan became extinct in the former half of 1580’s, and Hojyo clan finally seized Koga castle directly.

Koga castle after Koga Kubo

Koga castle had been one of the major castles of Hojyo clan, and they expanded it as an important basis. Koga castle is located on the long natural levee of Watarase river, and main areas formed line on the height about 1km long. West side of the castle was Watarase river, and southward and eastward of the castle was wide marsh. As above Koga castle was an impregnable fortress, but fell without resistance at the time of Odawara campaign by central ruler Hideyoshi Toyotomi (1534-1598) against Hojyo clan in 1590. Ieyasu Tokugawa (1543-1616) was newly appointed by Toyotomi government as a lord of Kanto region, and Koga castle had been continuously treated as significant location.

During Edo era, relative of Tokugawa clan or high class hereditary retainers such as Toshikatsu Doi (1573-1644), a grand minister of third Shogun Iemitsu Tokugawa (1604-1651), served as a commander of the castle. Bridgehead areas were newly built at outside of marsh, and three story turret as a substitute of main tower and other turrets were also built at main area. Palace of commander was also made in secondary area, and used for a lodge of Shogun at the time of visiting to Nikko Toshogu shrine.

Subsequent to Meiji revolution, all buildings were broken. In addition to this, to prevent the spread of mining pollution of Ashio copper mine located at the upstream of Watarase river, Meiji government spread Watarase river and built huge embankments. As the place of castle was public space and suitable for construction, most areas of castle  disappeared into riverbed and embankment river, and we can see only small sign of castle at the top of embankment. There remains no trace of central areas, but based on the result of infrared light investigation, the shape of the castle can be roughly grabbed. In addition to this, small part of clay wall and moat of bridgehead area still remain, and one gate of the castle was transferred at neighbor temple.

Related Castles

Sekiyado Castle -Castle coexisted with large rivers-

Pictures (click to enlarge)

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