was a Japanese castle structure located in what is now part of the city of Nankoku Kōchi Prefecture,

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. It was the original base of power for the Chōsokabe clan who were feudal lords of Tosa Province during the late Muromachi and Sengoku periods and famous as the birthplace of the warlord Chōsokabe Motochika. Its ruins have been protected as a National Historic Site since 2008.

Location

Okō Castle was located on a 97-meter mountain at the northern edge of the Kochi plain, next to the Kokubu River. It is located near the historic center of Tosa Province, as the

Tosa Kokubun-ji Tosa Kokubun-ji is a Shingon Buddhist Temple located in Nankoku, Kōchi, Japan. It is the 29th temple of the Shikoku Pilgrimage. It is also the Tosa Province Sōja shrine See Also * Tosa jinja (Tosa Province Ichinomiya is a Japanese h ...

and ruins of the Tosa provincial capital are in the vicinity. The main road from this area to Awa Province passes this castle, making it a strategic location for controlling the movement of people and goods in southern Shikoku.

History

The exact date of the castle's foundation is unknown but built in the

Kamakura period The is a period of Japanese history that marks the governance by the Kamakura shogunate, officially established in 1192 in Kamakura by the first ''shōgun'' Minamoto no Yoritomo after the conclusion of the Genpei War, which saw the struggle betwee ...

. Likewise, the origins of the Chōsokabe clan are uncertain. The clan claimed descent from the Hata clan and entered Tosa Province sometime in the 12th century as local administrators under the Kamakura shogunate, but were a minor clan. In the early Muromachi period, the Hosokawa clan became '' shugo'' of Tosa Province (along with Awa and Sanuki Provinces) and the Chōsokabe served as their retainers. However the Hosokawa were greatly weakened by the Ōnin War (1467-1477) and Tosa came to be governed by a coalition of seven local warlords, led by the Ichijō clan, a branch of the Kyoto nobility who had estates in western Tosa. The Chōsokabe attempted to capitalize on his unrest, but this resulted in an attack on Okō Castle by the neighboring Motoyama clan in 1508, and Chōsokabe Kanetsugu was forced to commit suicide. His son

Chōsokabe Kunichika was a powerful warlord in Tosa Province, Japan. He was the son of Chōsokabe Kanetsugu. His childhood name was Senyumaru (千熊丸).　 After his father Chōsokabe Kanetsugu was attacked by local lords and he killed himself in the Okō Castle ...

narrowly escaped from Okō Castle and several years later returned by

Ichijō Fusaie , son of regent Norifusa, was a '' kugyō'' or Japanese court noble of the Muromachi period (1336–1573). He was the second head of Tosa-Ichijō clan. He was born when his father Norifusa was in exile in Tosa Province from Kyoto Kyoto (; Ja ...

's help and recovered the clan's territories in the eastern part of the Kochi Plain. Kunichika sought revenge against the Motoyama clan, who controlled the western half of the Kochi Plain, and more importantly, the port facilities at Urato Bay. Kunichika began by seizing Nagahama Castle, a branch castle of the Asakura clan who were allied with the Motoyama in 1560. This marked the battle debut of his son Chōsokabe Motochika. On hearing of the fall of Nagahama Castle, the Motoyama responded by sending 1000 troops in a counterattack. Although the Chōsokabe had only 300 men, the fierce resistance led by Chōsokabe Motochika foiled the Motoyama attempt to retake the castle. Chōsokabe Kunichika died shortly after the battle. Motochika defeated an attempt by the Aki clan to take Okō Castle in 1563 and by 1570 had secured control over all of the Kochi Plain. By 1575 he had expelled the Ichijō clan and had united Tosa Province under his rule. Chōsokabe Motochika then invaded Awa and Iyo provinces, which he conquered by around 1580. Motochika was allied with

Oda Nobunaga was a Japanese ''daimyō'' and one of the leading figures of the Sengoku period. He is regarded as the first "Great Unifier" of Japan. Nobunaga was head of the very powerful Oda clan, and launched a war against other ''daimyō'' to unify ...

, but after the latter's assassination in 1582, he accelerated his campaign and had taken almost all of Shikoku by 1583. However, Toyotomi Hideyoshi viewed the Chōsokabe as an increasing threat and launched an invasion of Shikoku, decisively defeating the Chōsokabe at several locations, and limiting their rule to Tosa Province. Motochika moved the clan seat from Okō Castle to Urato Castle in 1591, and the castle was abandoned by 1598

Current

The castle is now only ruins, with low some stone walls, moats, and earthworks. The Kōchi Prefectural Museum of History was built in what was once the Third Enclosure. At the museum excavated artefacts from the castle are exhibited. The castle was listed as one of the Continued Top 100 Japanese Castles in 2017.

Gallery

File:Oko castle zenkei.JPG, Mountain Okō/Okō Castle File:Oko Castle 19.JPG, Tsumenodan compound (Honmaru compound) File:Oko Castle 20.JPG, Tsumenodan compound File:Oko Castle 16.JPG, Ninodan compound File:Okouzyou02.jpg, View from the Tsumenodan compound File:Oko Castle 09.JPG, Gate under the Tsumenodan compound File:Oko Castle 08.JPG, Dry moat File:Oko Castle 12.JPG, Stone wall of Sannodan File:Kochi Prefectural Museum of History 02.JPG, Kōchi Prefectural Museum of History

References

External links