Japan Castle Explorer: December 2017

Asakura Castle

-History of island hero (2) Watershed for island ruler-

Overview

Name: Asakura castle (Asakura-jo)
Alias:
Place: Asakura Kochi city, Kochi
Type: Mountain Castle
Built: 1520's
Remaining remnants: Stone walls, clay walls and moats
Title:

Brief History

Asakura castle (朝倉城) is built over Shiroyama mountain, one of about 100 meter height from hillside at the western edge of current Kochi city. Castle site is the place where Kagami-gawa river that forms Kochi plain flows from Kochi mountains turns from southward to eastward

Castle site is apart from current center of Kochi city, but formerly east half of current city area were under the water before land reclamation thus this place was appropriate place to manage western half of city area, Furthermore, it was close to the river basin of Niyodo-gawa river, which runs around middle part of Kochi prefecture. Therefore this place was convenient both for local domination and regional administration.

Origin of Asakura castle

It is said that Asakura castle was built by local lord Motoyama clan in 1520's. Motoyama clan was originally a traditional local lord of Motoyama area around the upstream of Yoshino-gawa river. The place itself exists in deep mountains, but as Yoshino-gawa river was used as a communication route from Tosa province toward eastern half of Shikoku island and central area, even though its limited economic resource its might have the basis of culture.

Motoyama clan was recorded in "Tosa Nikki", a diary written by Tsurayuki Kino (?-945?), a central cultural noble who was appointed as the governor of Tosa province (Kochi prefecture) in 10th century. Because of its geographical isolation Tosa province was calm at the conflict of Taira clan and Minamoto clan, then Motoyama clan became the retainer of Kamakura Shogunate.

After the fall of Kamakura Shogunate, Hosokawa clan which was the relative and high class retainer of Muromachi Shogunate seized the eastern half of Shikoku province. Hosokawa clan was also appointed as the governor of Tosa province, but indirectly managed it through major local lord such as Aki clan or Chosokabe clan.

Turbulence of Tosa province

On the other hand, in the latter half of 15th century, Ichijo clan which a distinguished noble of Kyoto city escaped from Battle of Onin and lived at Nakamura area, which was at the western edge of province. Based on its family status and wealth Tosa Nakamura port, Ichijo clan became the highest place lord of Tosa province outside of Kochi plain.

At the beginning of 16th century, Hosokawa clan once seized the authority of Muromachi Shogunate after the battle of Onin entered into severe internal conflicts. The army and people of Hosokawa clan retreated from Tosa province, and Tosa province at first experienced turbulent period.

At this time Kanetsugu Chosokabe (?-1508?), the grandfather of Motochika Chosokabe (1539-1599), grew their power under Hosokawa clan and coordinated the province. But other local lords such as Motoyama clan felt antipathy toward arbitrarily act of Kanetsugu, and waited for the chance to remove Chosokabe clan.

Strongest lord of Tosa plain

In 1508, looking at the retreat of Hosokawa clan, other local lords including Motoyama clan raised their army against Chosokabe clan and attacked their main base Oko castle (Kochi prefecture). Kanetsugu killed himself at the castle but let his son Kunichika Chosokabe (1504-1560) escaped from the castle.

Utilizing this opportunity, Shigemune Motoyama (1508-1555), the leader of Motoyama clan expanded their territory southward to the western half of Kochi plain. Motoyama clan built Asakura castle at the hill which can look down the plain, and built Urado castle at the east edge of the territory facing Urado bay.

At this time there were seven strong local lords at Tosa province, and apart from Ichijo clan, Motoyama clan advanced into was the first place of remaining six local lords around Kochi plain. Under Shigemune, Motoyama clan ruined Kira clan resided at the west of their territory, and fiercely conflicted against Ichijo clan. Asakuira castle was expanded along with the growth of Motoyama clan.

Structure of Asakura castle

Rough shape of Motoyama castle is like a spray bottle with narrow neck and long head spreads east and west ward. Main part of the castle is a oblong shaped area of about 100 meter long and 50 meter wide, at the east edge of the hill looks down Kochi plain. Main part of the castle consist of two upper area and surrounding terraces.

Outside of this central area, outer terraces were built between two vertical dry moats spread eastward and southward from core area, being protected by sharp slope and dry moats. This structure resembles Oko castle, the main base of Chosokabe clan, but far larger than that. There are primitive low height stone walls around central area even though most part might be added later for cultivation, and paths of the castle are well planned and secured by walls.

At the westward of core areas, ahead of narrow path, small outer fort which is about 20 meter diameter is built as a front fort of the castle. This part is also securely protected by the combination of vertical dry moat and horizontal dry moat, especially to westward where is connected to backside mountain. Total size of the castle is about 500 meter long and 200 meter wide, and larger than Oko castle and shows the power of Motoyama clan.

Collision against fatal rival

However, Kunichika Chosokabe (1504-1560), the survived son of Kanetsugu Chosokabe, returned as a lord of Oko castle under the support of Ichijo clan. Kunichika ruined surrounding small lords and merged with them, and gradually grew their power toward east half of Kochi plain. Under the coordination of Ichijo clan, Shigetatsu let his son marry with the daughter of Kunichika, and both clan once made peace.

In 1555, Shigetatsu Motoyama died in ill and his son Shigetoki Motoyama (?-?) succeeded Motoyama clan. Kunichika aggressively suppressed Motoyama clan by both of power and plot, and local lords under Asakura clan moved to Chosokabe clan. Motoyama clan was still stronger than Chosokabe clan, but as it had to cope with both of Ichijo clan and Chosokabe clan they fell behind.

In 1560, Kunichika Chosokabe fell Nagahama castle at the backside of Urado castle by plot. Angered Motoyama clan attacked Chosokabe army with larger soldier, but Motoyama army was finally broken by Chosokabe army and ran into Urado castle. At this battle Motochika Chosokabe (1539-1599) experienced the battle for the first time but showed significant activation.

Fall and afterward of castle

As Kunichika died in ill just after the battle, Chosokabe army once retreated. But Motochika who succeeded Chosokabe clan accelerated the attack toward Motoyama clan, and attacked Asakura castle in 1562. At this time Shigetoki Motoyama bravely fought and once rejected the attack of Chosokabe clan, but could not hold Asakura castle then retreated from Asakura castle next year.

Considering the power of Motoyama clan and well built structure of Asakura castle, Motoyama clan also had a qualification to unite Tosa province and Shikoku island. But father and son of Chosokabe clan well fought against strong Motoyama clan and opened their way to the ruler of Shikoku island. This battle was just the watershed of both clan for island ruler.

Motoyama clan which returned to mountainous area survived several year but finally surrendered to Chosokabe clan in 1571. Chikasige Motoyama (1545?-1587?), the last leader of Motoyama clan became the retainer of Nobuchika Chosokabe (1565-1587), the eldest son of Motochika, but died with his master at the battle of Hetsugi-gawa in 1587 and Motoyama clan

As the castle hill is not so high and has gentle shapes, most part of castle is used for cultivation then lost original structure and becomes off limit. But core part of the castle still keeps their shape covered by bamboos and bushes, along with front fort at westward. Compared with the castles of Chosokabe clan such as Oko castle or Urado castle it is not well treated, but remaining remnants showed possibility of Asakura clan for island ruler once surely existed.

Access

30 minutes walk from JR Shikoku Dosan-sen line Asakura station. 20 minutes drive from Kochi Jidoshado Expressway Ino interchange but no parking around castle site.